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北原 武, 古関 幸史, 森 謙治
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Novel efficient method of synthesizing medium-sized ring systems are developed. Thus the precursors, substituted phenyl-thioacetonitriles(12 and 23), prepared in optically active form from (+)-limonene, were submitted for cyclization with NaN(TMS)_2 in refluxing DME to afford ten-membered ring systems in excellent yield. Although the ambident anion derived from 23 could be alkylated at either α- or γ-position, only the desired α-alkylated product(24) with (E)-olefin was obtained exclusively. (-)-Dihydrogermacrene-D and (-)-germacrene-D, the latter of which is known as sex pheromone mimics of American cockroach (Periplaneta americana), were prepared by employing this method. Feasibility of this procedure to other medium-sized ring was demonstrated by using simple model compounds. Further application to the synthesis of periplanone-B, true sex pheromone of American cockroach will be discussed.
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高橋 孝志, 根本 尚夫, 北村 京子, 辻 二郎, 三浦 厳
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The intramolecular alkylation of carbanion, generated from protected cyanohydrin and subsequent mild treatment with acid and base of cyclized products lead to cyclic enones. These overall transformations give the labile enone and 1,5-diene systems without isomerization of double bonds. This method of alkylation generates monocarbanion and the reaction is rapid and irreversible, and hence requires short reaction time. The method was successfully applied to the syntheses of (±)-Acoragermacrone (16), Germacrone (29), Humulene (38), and (±)-Mukulol (28).
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浅岡 守夫, 石橋 恵治, 柳田 昇, 武井 尚
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Two-step synthesis of γ-ylidenebutenolides has been achieved by dehydration or dealkoxylation of the reaction products of various aldehydes, ketones, and acetals with 2-(trimethylsiloxy)furan in the presence of tin(IV) chloride. This method was applied to the synthesis of 7, 10, and 13. The synthesis of (±)-eremolactone was also examined. In the presence of titanium(IV) chloride, siloxydiene(17) reacted with mesityl oxide to give four diastereoisomeric adducts which structures were presumed as 29a-d. The major isomers(29a, b) gave 30a and 30b respectively by sodium borohydride reduction, though the other two (29c, d) afforded reduced products of acetyl group. Dehydration of 30a followed by functional transformation afforded aldehyde 35a, which was converted to ylidenebutenolide 37a-Z. The double bond migrated comound 38a-Z was revealed to be 9-epimer of (±)-isoeremolactone based on the H^1-NMR spectral data. Therefor the structure of 37a-Z was presumed as shown. The end-exo isomerization of 31a, 35a, and 37a or the transformation of 30b to (±)-eremolactone is under investigation.
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相見 則郎, 川田 和広, 長郷 裕子, 坂井 進一郎
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Thysanolactone (1) is a natural triterpenoid compound isolated by us from a Rubiaceous plant, Thysanospermum diffusum Champ. var. longitubum Ohwi, native in Okinawa, Japan. This compound was found to have a unique 2,3-seco-moretane skeleton and the unprecedented oxygen-containing ring system forming the A ring part as shown by the structure (1). Chemical conversion of an easily available natural compound with the biogenetically fundamental structure type to this unique compound was undertaken. Dihydrothysanolactone (8) was derived from hydroxyhopanone (7) in 10 steps as shown in Chart 1. This conversion clarified the absolute configuration of (1). An unnatural type stereo isomer (23) was also prepared. (Chart 2). A study on the partial synthesis of (1) from the same starting material was then made. Norketone (32) prepared from (1) was found to give (1) in a good yield by use of Wittig reagent. Therefore (32) was chosen as the objective molecule of this transformation. This attempt has proceeded so far as shown in Chart 4. Further work is now under way.
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福本 圭一郎, 井原 正隆, 宍戸 宏造, 千尋 正利, 斎藤 忠正, 亀谷 哲治, 本多 利雄
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Synthetic studies on a carbon framework of quassinoid klaineanone (1) and quassinoidal antileukemia agent bruceantin (2) have been carried out. The key step in this approach was an stereoselective intramolecular cycloaddition of the o-quinodimethanes (4), (27), generated in situ from the thermolysis of the benzocyclobutenes (18 and 34). The compound (18) was prepared from norcamphor via stereoselective methylation of the lactone (7). The cycloadduct (20) was converted into the tetracyclic lactone (22) whose structure was confirmed by X-ray analysis. The C-8 methyl analog (24) which is a klaineanone model compound was also synthesized. The compound (27) was prepared using a methoxyallene cyclization reaction. Stereoselective introduction of C-2 unit into the cycloadducts (39 and 47) was eventually achieved in high overall yield by a two step procedure: (i) Horner-Emmons reaction; (ii) NaHTe reduction. The construction of D-ring of the pentacyclic bruceantin model compound (25) is under way.
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原田 宣之, 岩渕 淳, 横田 洋一, 宇田 尚, 越智 雅光, Nina C. Gonnella, 中西 香爾, Victor S. Ma ...
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A new chiroptical method for determining the absolute configuration of allylic alcohols is described. The CD exciton chirality method can be extended to the system of allylic alcohol benzoates, nondegenerate systems composed of two different chromophores, i.e., benzoate with an allowed π→π^* transition at 230nm and C-C double bond with an allowed π→π^* transition around 195nm. Since these transitions are both polarized along the long axes of the chromophores, the exciton theory predicts that if the two long axes of benzoate and double bond chromophores constitute a positive exciton chirality, i.e., right-handed screwness, the first Cotton effect at longer wavelengths (230nm benzoate Cotton effect) is positive. On the other hand, if the allylic benzoate constitutes a left-handed screwness, the 230nm benzoate Cotton effect should be negative. The present method was confirmed by the CD spectra of a number of compounds. The absolute configuration of isoamijiol 34, a diterpene with dolastane skeleton isolated from a marine alga Dictyota linearis, was determined by application of this method. The present method has been also extended to acyclic allylic alcohols.
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安東 政義, 山岡 弘明, 高瀬 嘉平
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Guaianolides are a rapidly expanding group of natural products, comprising to date ca. 200 varieties. Because of their high biological activities, their efficient syntheses are the synthetic challenge which has received much attention during the past few years. We envisioned a general synthetic approach to the guaianolides which consisted of the solvolytic rearragement of the appropriately functionalized eudesmanolides such as compounds (8) and (21), which were prepared from α-santonin in 13% and 20% yields, respectively. Solvolytic rearrangement of 8 gave a mixture of endo- and exocyclic olefins (9 and 10). The selective epoxidation of 9 in this mixture with 0.5 molar equivalent of m-CPBA gave 10 and stereoisomeric epoxides (11) and (12) in 40%, 22%, and 29% yields, respectively. The resulting exocyclic olefin (10) was converted into a diene (16) in 66% yield in 3 steps. The regioselective epoxidation of 16 gave a 4: 1 mixture of an α-epoxide (17) and the corresponding β-epoxide (18) in 58% yield. The treatment of this mixture with Al(iPrO)_3 in refluxing toluene gave an α-allyl alcohol (19) which was converted to C_3-epizaluzanin C (2) in 15% overall yield. The diene (16) has already been converted to estafiatin (1) by Greene et al. The solvolytic rearragement of (21) and successive hydrolysis of the resulting inseparable mixture of acetates (22, 23, and 24) gave a mixture of α-allyl alcohols (19, 25, and 26). The treatment of this mixture with acetic acid in the presence of triphenylphosphine and diethyl azodicarboxylate gave a mixture of β-acetates (27, 28, and 29). Phenylselenenylation and successive hydrolysis of the resulting diselenide (30) gave 32 in 26% yield. Oxidative syn-elimination of 32 gave zaluzanin C (3).
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柴崎 正勝, 山崎 まゆみ, 池上 四郎, 伊関 克彦
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A simple, highly stereocontrolled synthesis of (+)-Hirsutic acid 1, a representative of a novel tricyclic sesquiterpene class, is described. In the first part of this presentation, the asymmetric syntheses of (1S, 5R, 6S)-6-hydroxybicyclo[3,3,0]octan-3-one, (+)-2, a key intermediate for the present synthesis, are reported. One route consists of the conversion of the known hydroxy-ester, (+)-27, to optically pure (+)-2 by employing a series of efficient reactions. The other route, which is capable of providing (+)-2 in large quantities and high enantiomeric purity, involves the reaction of dl-3 with (+)-di-3-pynanylborane as a key step. Using this reaction, followed by oxidation and hydrogenolysis, (+)-2 with high optical purity is readily obtained as a major product. The undesired ketone, (-)-5, is also convertible to (+)-2. In the second, the highly stereocontrolled transformation of (+)-2 with 80% optical purity to (+)-1, which includes a methylene transfer reaction with very high stereochemical control(>98%) by the participation of a rather remote hydroxy group as a key step (7→10) is presented. As a result, optically pure (+)-1, [α]^<25>_D+114°(CHCl_3), m.p. 174°〜176℃, could be obtained by recrystallization from ether for two times. In the third, an alternative route to (+)-1 from (+)-2, which involves the chelation-controlled methylation of an ester enolate from the sterically more crowded face (14→16) as a key step, is discussed.
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鈴木 正昭, 川岸 俊雄, 鈴木 建彦, 柳沢 章, 野依 良治
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A very short chiral synthesis of primary prostaglandins is disclosed. The key operation is the vicinal carba-condensation with α,β-unsaturated ketones which is based on the conjugate addition of a stoichiometric amount of an organo-copper reagent (formed from an organolithium, copper(I) iodide, and tributyl-phosphine in 1:1:2-3 mol ratio) and trapping of the resulting enolate with an aldehyde. The three-component coupling reaction proceeds in a high yield and in a regiospecific fashion. Combination of (R)-4-tetrahydropyranyloxy-2-cyclopentenone, (S)-(E)-1-iodo-3-tetrahydropyranyloxy-1-octene, and 6-methoxy-carbonylhexanal by this method leads directly to methyl ester of 7-hydroxy-11, 15-O-bis(tetrahydropyranyl)-PGE_1. Dehydration, zinc reduction of the resulting Δ^<7,8> derivative, and removal of the tetrahydropyranyl protective groups gives (-)-PGE_1 methyl ester. Combination of (R)-4-t-butyldimethylsiloxy-2-cyclo-pentenone, (S)-(E)-3-t-butyldimethylsiloxy-1-iodo-1-octene, and 6-methoxy-carbonyl-2-hexynal gives methyl ester of 5,6-dehydro-7-hydroxy-11,15-O-bis(t-butyldimethylsiloxy)-PGE_2. Removal of the 7-hydroxy group is effected by thiobenzoylation followed by reduction with tributyltin hydride to afford a key common intermediate for PG synthesis. PGE_2 methyl ester is obtained by catalytic hydrogenation over Lindlar catalyst, followed by removal of t-butyl-siloxy groups with hydrogen fluoride-pyridine. PGF_<2α> methyl ester is also derived by stereoselective reduction of the 9-keto group, partial hydrogenation of the triple bond, and desilylation.
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平間 正博, 上井 充子
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Compactin 1a (ML-236B) has become one of the prime targets aimed by a number of synthetic organic chemists since 1976, because of its high hypocholesterolemic activity and unique structural feature. A convergent and enantioselective synthesis of 1a has been achieved via asymmetric intramolecular Diels-Alder reaction of the acyclic (E,E,E)-trienone 4 leading to trans-octalone 3, which was a versatile intermediate to give all related compounds (1a, 1b, 2a and 2b) in the compactin family through the simple manipulation of the B ring functionality. 4 embodied the whole carbon-linkage necessary for 1a, and its intramolecular Diels-Alder reaction was considered to be a viable approach for the stereo-controlled construction of the trans-octalone. Our synthetic point based on the utilization of the allylic chiral center (C13) to control the approach of the dienophile from a single diastereotopic face of the diene. The four asymmetric centers (C8, C9, C14 and C17) with correct absolute configurations were expeditiously introduced by a choice of S configuration at C13-chirality. 4 was readily accessible by the Wadsworth-Emmons coupling of the optically active segments A (5) and B (6). Preparation of the acyclic 1,3,5-triol 6, masked form of the sensitive β-hydroxy-δ-lactone system, rested on a combination of a convenient and highly asymmetric reduction of β-keto acid 10d with baker's yeast and a subsequent regio- and stereoselective functionalization (i.e. 1,3-asymmetric induction) of the chiral homoallylic carbamate 13c using the novel carbamate-mediated iodocyclization. The synthesis of 5 in its optically active form was accomplished by the elaboration of the readily available 4S-γ-lactone 8.
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小林 和裕, 甲斐 真里子, 西出 喜代治, 檜山 爲次郎
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A new method is reported for the synthesis of amino sugars such as daunosamine, 3-epidaunosamine, acosamine, and ristosamine, the sugar moieties of anthracycline antibiotics. The process consists of three key steps: (1) preparation of 2,3-dialkoxy-butanenitriles with the defined configuration, (2) introduction of C_2 unit into the nitriles, (3) reduction of β-aminoacrylates to create C-3 amino group having the desired stereochemistry. The first problem was dissolved by starting with L(+) tartaric acid and/or S(+) lactic acid. These were successfully transformed into (2S,3S)- and/or (2R,3S)-2,3-(alkylidenedioxy)butanenitrile. The second synthetic obstacle was kicked off by a new transformation of nitriles into β-aminoacrylates with the aid of the magnesium enolates of acetic acid esters. Final problem, stereoselective hydrogenation of the β-aminoacrylates, was accomplished by acetylation of the substrates followed by catalytic hydrogenation (1 atm) with PtO_2 catalyst in ethyl acetate solvent. Thus, (2S,3S)-2,3-(cyclohexylidenedioxy)butanenitrile was converted into N-acetyl-3-epidaunosamine methyl ether and the daunosamine derivative with ca 4: 1 ratio, whereas (2R,3S)-2,3-(cyclohexylidenedioxy)butanenitrile into acosamine derivatives with high degree of stereoselectivity.
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秋田 弘幸, 古市 昭也, 越地 弘子, 掘越 弘毅, 大石 武
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In the field of synthesis of polyoxoantibiotics or the related polyfunctional natural products, the use of optically active compounds as a starting material is known to be quite advantageous. We now report the synthesis of optically active I, having the 2-methyl, 3-hydroxy moiety involved in I, based on the asymmetric reduction of the corresponding α-methyl β-keto ester II by microorganisms. 1. Microbiological asymmetric reduction of Dimethyl 2-methyl-3-oxo succinate 1 and Diethyl 2-methyl-3-oxo succinate 12 Asymmetric reduction of 1 by Saccharomyces cerevisiae gave the syn-2(2R,3R; 65 %ee) and the anti-3(2S,3R; 20 %ee). The stereostructure and the optical purity of the products was determined by means of 400MHz NMR spectroscopy. 2. Microbiological asymmetric reduction of methyl 2-methyl-3-(2-furyl)-3-oxo propionate 15 In order to obtain four functionalized chiral synthons (16, 17, 18, 19), asymmetric reduction of 15 was carried out. Kloeckera saturnus was found to give (S)-alcohols (16 and 18), while Saccharomyces delbrueckii or Saccharomyces fermentati afforded the opposite (R)-alcohols (17 and 19). Mass production of each isomers was undertaken and both chemical yield and optical yield (16; 83 %ee, 18; 73 %ee, 17; >99 %ee, 19; 98 %ee) were improved. In these cases, syn(16, 17)-anti(18, 19)-isomers are separable by usual Silica gel chromatography. 3. Determination of absolute structure of Oudemansin 25 For the purpose of determining an absolute structure of Oudemansin 25, the synthesis of optically active intermediates 29 or 30 was undertaken. Treatment of Me ester 26 with Saccharomyces cerevisiae gave the syn-29(2S,3R), while reduction of Et ester 27 with Candida albicans afforded the antipode 35(2R,3S). Optical yields of 29 (>99%ee) and 35 (97%ee) were extremely high in both cases.
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高岩 明裕, 山下 恭平
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Gregatins are a family of phytotoxic metabolites isolated from Cephalosporium gregatum and was also isolated from Aspergillus panamensis as antibacterial substances. The proposed structure (3) (Fig 1) was revised to (1) by Pattenden et al. We also reached to the same conclusion by the synthesis of (3) and the comparison of the spectral data of the synthetic tetronic acid derivatives (6a〜7a) and that of 5-methoxy-3(2H)furanones (6b〜9b). This paper describes the determination of the C-4 configuration in gregatin A, B, D and aspertetronin A, B; total synthesis of natural (S)-(+)-gregatin B and clarification of the stereochemistry of related tetronic acid, vertinolide. (1) γ-Valerolactone-γ-carboxylic acid (11) was utilized efficiently for the synthesis of chiral 5,5-disubstituted tetronic acid (14), (22) and (47). (2) The stereochemistry of C-4 of aspertetronin A and vertinolide was clarified as (R) and (S), respectively, by the synthesis of the chiral tetronic acid (4) and (29) derived from natural ones. (3) Gregatin B was synthesized from γ-valerolactone-γ-carboxylic acid (11) via acetoacetoxy ester (46), α-acetyl tetronic acid (47) and final methylation with diazomethane-BF_3-etherate. Starting from (S)-(-)-acid (11), natural (S)-(+)-gregatin B was obtained.
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長尾 善光, 池田 高夫, 井上 武久, 藤田 栄一
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The most interesting targets for synthetic chemists have been focused on the biologically active natural products such as macrolide, macrolactam, polyether, and β-lactam antibiotics. These compounds have complicated chemical structures possessing several asymmetric carbon atoms. Usually, only one enantiomer exhibits the desirable activity. Therefore, optically active, simple acyclic compounds have been utilized as the starting materials in their total syntheses. Use of a symmetrical molecule is one of the important strategies in the asymmetric synthesis, because it may be a benefitable precursor for an enantio-convertible chiral compound by utilizing its own bifunctionality. We have designed and developed a novel, nonenzymatic procedure: a highly selective asymmetric induction into a symmetrical, acyclic molecule such as 3-methylglutaric acid (6) or meso-2,4-dimethylglutaric acid (22) via an aminolysis of 4(R)-MCTT diamide 7 or 25, respectively. This new chemical asymmetric synthesis is not only useful as a practical synthetic tool for the synthesis of antibiotics but also as an aid in the elucidation of the action of enzymes such as α-chymotrypsin and pig liver esterase.
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千田 憲孝, 宮下 正昭, 吉越 昭
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The chiral synthesis of (+)-thienamycin (1) starting with readily available D-glucosamine (3) has been described. Protected glucosamine 4 was submitted to photo-induced reductive deacetoxylation to give the 3-deoxyglucosamine derivative 5, which was then transformed into aldehyde 9 as shown (Scheme 2). Homoaldehyde 11 obtained from 9 via the Wittig reaction was oxidized and then hydrolyzed with alkali to give β-amino acid 14. The amino acid provided β-lactam 15 by treatment with (PyS)_2-Ph_3P. After N-silylation of 15, the hydroxyl group in the product 16 was reductively removed to give 18, and the hydroxyethyl side chain was introduced on its β-lactam ring by condensation with acetaldehyde yielding 6S,8R-isomer 19a as the major product, along with other diastereomers 19b〜d (Scheme 3). The undesired diastereomers 20b〜d, after O-silylation of the reaction mixture, were separated from the major product 20a and the former isomers were effectively recycled to the desired alcohol 19a as shown. The bis-silylated β-lactam 20a was debenzylated and regioselective oxidation of the resulting diol 22 by Pt-catalyzed autoxidation afforded hydroxy acid 23 (Scheme 4). The benzyl ester of 23 was oxidized to β-keto ester 25 ([α]_D-48.5°), which was spectroscopically identified as the known key intermediate for (+)-thienamycin (1).
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吉岡 正人, 中井 久郎, 大野 雅二
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Bactobolin (1a), a new congener of actinobolin (1b), was recently isolated from the culture broths of a Pseudomonas sp.^<1,2> These antibiotics 1a and 1b have a common bicyclic skeleton but differ considerably in their biological activity, especially in antitumor activity, the former being much stronger than the latter. We wish to report here a highly stereoselective synthesis of the common skeleton 17 by the intramolecular Diels-Alder reaction of the triene 3 containing (Z)-diene and an asymmetric carbon at the pentadienylic position. Our synthetic strategy is based on the following considerations: (1) the intramolecular Diels-Alder reaction of a (Z)-diene will occur from a single diastereomeric face of the dienophile, (2) a desirably bulky substituent (a chiral center) at the pentadienylic position will further amplify to select a preferred single transition state by substantial nonbonded interactions with the terminal vinyl group of the diene, (3) thus the chiral diene derived originally from L-threonine will give the desired asymmetric carbons through the key reaction, (4) Iodolactonization and transformation of γ-lactam 2 to δ-lactone 15 will afford the common precursor to 1a and 1b. The experimental results showed that a series of reactions proceeded efficiently and the stereochemistry of a product 18 was established by X-ray analysis.
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及川 裕二, 西 孝夫, 米光 宰
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An approach to the total synthesis of erythronolide A from D-glucose has been investigated. For the construction of segment i, D-glucose was converted to the olefin 6 via enone 4 in moderate yield. Then, the compound 6 was osmylated to give stereoselectively(23:1) the diol 7, which was proved to have the desired stereochemistry based on the NMR spectrum of 8 obtained from 7 by acid treatment followed by acetylation. 7 was then converted to the aldehyde 13 in good yield. However, several attempts to synthesize 15, which has all chiral centers of segment i, were found to be unsuccessful. An alternative way to prepare 15 is now under investigation. The synthesis of segment iii was completed as follows. 28 derived from 1 was converted to 30, which was then hydroborated stereoselectively(6.6:1) to give 31. The hydroxymethyl of 31 was transformed to the methyl via mesylation followed by the reduction with lithium aluminum hydride to give 32, which was converted to 34 via 33 in five steps. The cleavage between C-5 and C-6 of erythromycin A to obtain segments i and ii for the structural confirmation was successfully completed as follows. 9-Dihydroerythronolide 36, obtained from erythromycin A by the reported method was converted to 42 in 65% yield. Protection of 11,12-diol in 42, followed by the lithium aluminum hydride reduction gave 48, which was transformed easily to the tetraol 50 in three steps Finally, 50 was cleaved by lead tetraacetate to afford 51 and 52 in quantitative yield.
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本田 昌徳, 香月 勗, 山口 勝
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Micromonospora griseorubida sp. nov. produces a group of sixteen-membered macrolide antibiotics which are named mycinamicin I-V and protomycinolide (1). Synthetic studies on 1 and the aglycone (2) of mycinamicin V were undertaken by using the asymmetric epoxidation of allylic alcohol as the key step. meso-2,4-Dimethylglutaric anhydride (3) was transformed into the allyl alcohol (6) by a conventional way. Ti-catalysed epoxidation of (6) with TBHP in the presence of (+)-DIPT gave 7, as a 1:1 mixture of two diastereomers, optical purity of each being determined to be >95% ee after separation of a portion through a Lobar column. Regiospecific reduction of the mixture (7) by Red-al, followed by successive acetylation, deprotection, oxidation, and hydrolysis gave a mixture of lactone alcohols (10). 10 was then converted into the ester (14) which was separated from the undesired isomer, and further transformed into an ylide (16), as a common intermediate for C_1-C_<10> part (segment A) of 1 and 2. The lactone alcohol (10) was also transformed into (+)-Prelog-Djerassi lactonic methyl ester in two steps (overall 18% from 3). The C_<11>-C_<15> segments (22 and 27) for 1 and 2 (segment B's) were constructed as shown in the sequences 17→22 and 23→27, respectively, again taking advantage of the above epoxidation. Condensation of the segment A with the segment B's and subsequent steps leading to 1 and 2 are now in progress.
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植村 元一, 嶽 一彦, 林 雄二
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(3-Methoxybenzyl alcohol)tricarbonyl chromium complex 8 and (2-substituted-7-methoxy-1-tetralol)chromium complexes 9 are selectively lithiated at the 4-position and 6-position, respectively, by the treatment with n-BuLi/TMEDA. The regioselectivity of this lithiation increase with increasing bulkiness of the butyllithium reagent employed. Since the direct lithiation of the corresponding chromium free arenes, 1, 2 and 3 proceeds at the 2- and 8-position, respectively, this different regioselectivity of the lithiation is useful for the synthesis of substituted arene compounds. The difference is explained by the relative configuration of the tricarbonyl chromium group in the π(arene)Cr(CO)_3 complexes, and the electric repulsion effect. On the other hand, the chromium complexes of arenes without free hydroxyl group, such as benzylmethyl ether or ethyleneacetals of 3-oxygenated benzaldehydes, are lithiated at the 2-position preferentially, in contrast to the above results with benzyl alcohol derivatives. The synthetic studies on Rabelomycin 21 are in progress by using this regioselective lithiation of π(arene)tricarbonyl chromium complexes.
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西山 繁, 鈴木 伴子, 山村 庄亮
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Bastadins, metabolites from the Verongid sponge Ianthella basta, constitute acyclic (1, 2, and 3) and novel hetero 28-membered lactam (4) compounds derived from four brominated tyrosine units. The biomimetic approach to the total synthesis of 1, 2, 3, and 4 using phenolic oxidation by thallium (III) salt as well as anodic oxidation in key steps was successfully carried out, and each geometry at the oxime C=N double bonds in acyclic bastadins was unambiguously determined to be anti. The 26-membered lactam congener 31 was also synthesized.
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高野 誠一, 世永 雅弘, 笠原 千義, 田村 伸彦, 後藤 恵美子, 内田 渡, 平間 道康, 畑山 範, 小笠原 国郎
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Enantioselective syntheses of a variety of natural products using a chiral glycerin derivative ((S)-1) as a common chiral synthon obtained from D-mannitol have been accomplished. The chiral glycerin derivative ((S)-1) has been converted into γ-substituted γ-butyrolactone or α,γ-disubstituted γ-butyrolactone derivatives (3), via the epoxide (2) or the iodide obtained from the glycerin ((S)-1) acetonide, which in turn alkylated or protonated in highly stereoselective fashion to give stereodefined γ-lactone intermediates. From these intermediates, a variety of natural products, such as secoiridoid monoterpenes (-)-semburin (4) and (-)-isosemburin (5), a corynanthe indole alkaloid (-)-antirhine (6), iboga indole alkaloids (+)- and (-)-cleavamine (7), a carbapenem intermediate (8), an eburnamine indole alkaloid, (-)-eburnamenine (10), a bisabolene sesquiterpene (+)-nuciferal (12), and a physostigma indole alkaloid (-)-physostigmine (13), have been synthesized enantioselectively.
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中川 昌子, 袖岡 幹子, 谷口 幹雄, 山口 啓一, 日野 亨
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A new synthetic approach to tryptoquivalines which involves the oxidative double cyclization of N-acyltryptophan derivative 5 has been investigated and following results were obtained. I. Synthesis of the imidazo (1,2-a) indole-spirolactone 12 Acylation of indole nitrogen with an amino acid is little investigated in comparison with that with ordinary acylating agents such as Ac_2O and RCOX. Acylation of benzyl Indole-3-propionate 9 with N-methoxycarbonyl-α-methylalanine p-nitrophenyl ester 10 in DMF-NaH successfully provided the N-acylindole derivative 11a in 70% yield. The yield of 11a increased up to 84% when the reaction was performed in CH_3CN in the presence of 18-crown-6/(i-Pr)_2NEt/KF. The key intermediate 11b obtained by debenzylation of 11a was subjected to bromination with NBS in CH_2Cl_2 to give the expected compound 12 (20%) whose stereochemistry was unequivocally established by x-ray analysis to have the same stereochemistry with the natural products. The removal of methoxycarbonyl group of 12 by Me_3Sil was not successful and 18 was obtained. The similar cyclization of 19 to the corresponding spirolactone was also carried out. II. Synthesis of the quinazolinone 5 The reaction of 20 and isatoic anhydride 21 in benzene gave the amide 22 which was readily converted to 23 by heating with orthoformate and a catalytic amount of TsOH in excellent yields. Treatment of 23 with 10' under similar conditions as above yielded 24 in 68% yield.
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木口 敏子, 橋本 千代美, 内藤 猛章, 二宮 一弥
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Reductive photocyclization of enamides, which is carried out by the irradiation on an enamide in the presence of a large excess of sodium borohydride at low temperature, has been successfully applied to the synthesis of ergot alkaloids including lysergic acid, based on the preliminary study on the synthesis of some benzo(f)quinoline derivatives. A general synthetic route with a great potentiality of application toward a group of ergot alkaloids was established through the synthesis of some benzo(f)quinoline derivatives (16, 29, 33, and 35) which are regarded as the despyrrole analogs of ergot alkaloids. Reductive photocyclization of enamides (2, 10, and 22), prepared by acylation of 2-tetraloneimine (1) with methacryloyl, 3-methoxy-2-methylacryloyl, and 3-furoyl chlorides, afforded the skeletal structures of alkaloids in one step respectively, which were then structurally modified in order to introduce a double bond and/or functional groups in the ring C. Based on the synthetic route thus established, total synthetic works of ergot alkaloids were carried out using the tricyclic imine (5) as the common starting compound. As a result at the moment, total synthesis of 6,8-dimethylergolines and lysergic acid along with 2,3-dihydroagroclavine (21) and 2,3-dihydroisofumigaclavine (45) was achieved.
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新間 信夫, I. Kompis, V. J. Gruenman, M. R. Uskokovic
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Stereoselective synthesis of the metabolites (2 and 3) of 7'-trifluoromethyl dihydrocinchonidine (1), antiarrhythmic agent, has been achieved as described below. The key synthon (14) of guinuclidine moiety of 2 (C_<10>-R) was synthesized starting from loganin (4). Reductive amination of the aglycone of 4 followed by the successive treatments of 5 with 3N HCl, NaBH_3CN, and PhCOCl gave 8. The Baeyer-Villiger oxidation of 10, Jones' oxidation product of 8, afforded the lactone (12), which was transformed to 14 in 3 steps. Another synthon (30) was synthesized from 1S-(3-pyridyl)ethanol (15). Hydroboration of the key intermediate, E-olefine (27) prepared from 15 in 7 steps, gave the C_<10>-S lactone (28), which was converted to the synthon (30). Condensation of 30 with 7-trifluoromethyllepidine (32) afforded the ketone (34). Then 34 was converted to the olefine (40) via 37 and 38. Reduction of 40 with DIBAH followed by refluxing the resulting amine (42) in 10% H_2O-MeOH gave the cyclized product (44a,b). Finally, stereospecific hydroxylation at C-9 of 44a,b with oxygen and desilylation of (45a dnd 45b) gave 10S-metabolite 3 and the isomer 50. In a similar manner, 10R-metabolite (2) was also synthesized from 14 and 32.
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D. J. Hart, 金井 健一
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A total synthesis of dl-gephyrotoxin (1), an alkaloid isolated from skin extracts of the Columbian frog, Dendrobates histrionicus has been achieved. A total synthesis of dl-dihydrogephyrotoxin (2), a structure tentatively assigned to a minor Dendrobatid alkaloid, is also described. Reduction of 10 followed by Mitsunobu reaction gave 13. The first two steps of the syntheses established the stereochemistry at three asymmetric centers (C-5a, C-6, C-9a) of 1 and 2. The C(3a) asymmetric center was established via cyclization of N-acyliminium ion derived from 16 [16→17]. The undesired C(5) functionality was removed using the procedure of Barton [17→18→19→20]. The C(1) sidechain was introduced as follows. Eschenmoser sulfide contraction of 21 gave 22. The bulky silyl group at C(6) sidechain of 32 directed the stereochemical course of the catalytic hydrogenation [32→35]. The cis-enyne moiety was introduced to C(6) using the method of Yamamoto [37→38]. DIBAL reduction of 38 followed by desilylation gave dl-1. A combination of diene synthesis developed by Matteson and DIBAL reduction was applied to the synthesis of dl-2 [37→40→41→2]. An interesting feature of these syntheses is that no protection-deprotection sequences were required.
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奈良坂 紘一, 坂倉 俊康, 内丸 忠文, 守本 潔
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A total synthesis of a 12-membered bislactonic pyrrolizidine alkaloid, (±)-integerrimine (1), has been achieved. Integerrinecic acid monoester (6), the acid part of integerrimine, was synthesized stereoselectively starting from 2-methyl-2-cyclopentenone. Retronecine (3) was prepared according to a modified method of the Geissman's route, and the primary alcohol was protected as silyl ether (7). The acid component (6) was converted to an acid anhydride (8), and then 8 was treated with lithium salt of 7 and a catalytic amount of N,N-dimethylaminopyridine to give a desired ester (9). This ester (9) was too unstable under acidic conditions to be deprotected selectively to yield the hydroxy acid (10). Therefore, new esterification reaction was developed based on the concept of activatable protective group, and it was found that treatment of alkylsulfonylalkyl esters of carboxylic acids with lithium alkoxides afford the corresponding esters in good yields. (±)-Integerrimine (1) was synthesized successfully by the application of this method to the lactonization step.
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村井 章夫, 吉沢 結子, 佐藤 慎吾, 勝井 信勝, 正宗 直, 佐藤 章夫
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The present paper describes biosynthetic studies on phytoalexins produced in diseased potato tubers (S. demissum×S. tuberosum), using synthetic (±)-[8,8-^2H_2]solavetivone (2a) and (-)-[12,12-^2H_2]rishitin (1a). The result summarized in Scheme 5 indicates that (i) natural (-)-(2) is metabolized into (-)-(1) via (+)-lubimin (16) and (+)-oxylubimin (17), while synthetic (+)-(1) does not undergo such enzymatic reactions, (ii) (-)-(2) would be a key intermediate for formation of (-)-(1) and (-)-phytuberin (3), two major phytoalexins in potato, (iii) (-)-(1) is metabolized separately into rishitin M-1 (4), M-2 (5), and M-3 (14) [and M-4 (15)], (iv) transformation of (-)-(1) into (-)-(5) in vivo proceeds in stereospecific manner, when the NIH shift and the deuterium isotopic effect in chemical shift were observed, and (v) the D_2-content of stress metabolites formed on incubation of the labelled compounds (2a) and (1a) (both D_2-content, ca. 100%) decreased clearly, indicating that some of the stress compounds are a stress itself, i.e., rishitin produces rishitin. Detailed examination of the deuterium content leads us to propose that phytoalexins accumulate in the area where phytoalexins are produced ("product-staying hypothesis" rather than currently accepted "transportation hypothesis").
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藤本 善徳, Ching-Sih Chen, Charles J. Sih
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The mechanism of microbial degradation of the branched hydrocarbon side chain of phytosterol, e.g. sitosterol (2) and campesterol (3) was investigated employing Mycobacterium sp. NRRL B3805. From the experimental results using intact cells, the intermediacy of 26-hydroxysitostenone (7), 3-oxostigmast-4-en-26-oic acid (8) and 3-oxo-4-cholenic acid (5) was established. Cell free studies gave us the following conclusive results. Exposure of [28-^<14>C]-8 to the cell free extracts resulted in the formation of radioactive propionic acid with all of the radioactivity residing in carbon 2 of the molecule. When unlabelled 8 was again incubated in the presence of [^<14>C]-NaHCO_3, 5% of the radioactivity was found in propionic acid with all of the radiolabel residing in carbon 1. When this cell free system was incubated with 3-oxoergost-4-en-26-oic acid (16) and [^<14>c] -NaHCO_3, radioactive acetic acid was formed. Degradation of the molecule revealed that carbon 1 contained most of the radioactivity. Hence, cleavage of the phytosterol side chains by this microorganism involves the incorporation of CO_2 onto the C-28 position of the phytosterol molecules, followed by carbon-carbon bond fission at C-24, 25 and C-24, 28 as shown in scheme 2.
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井上 謙一郎, 上田 伸一, 苗代 英一, 木戸 正, 漏留 信晴, 井上 博之
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The biosynthesis of naphthoquinones (10, 12, 14 etc.) with an inverted isoprenyl group and anthraquinones (11 and 17) of Streptocarpus dunnii was studied using precursors labeled with stable isotopes and cell suspension culture of the plant. The administration of [2'-carboxy-^<13>C]-4-(2'-carboxyphenyl)-4-oxobutanoic acid (OSB) to the cell cultures revealed that all these quinones are biosynthesized via OSB, and that anthraquinones are not formed via prenylation on the position corresponding to C-3 of OSB as in Rubiaceous plants, but formed via prenylation on the position corresponding to C-2. Feeding experiments with [7-^2H]-lawsone (19) and its prenyl ether (20) further demonstrated that naphthoquinones are formed via these compounds. On administration of 20, the overflow production of [7-^2H] -2-hydroxy-3-(1,1-dimethylallyl)-1,4-naphthoquinone (22), the Claisen type rearrangement product, was observed, which was caused by the abundant exogeneous precursor (20). Furthermore, on administration of 19 or 20, tectoquinone (23) was also isolated as an overflow product owing to the feedback control. On the basis of these results the biosynthetic pathway of the quinones in S. dunnii cell cultures were presumed to be shown in Scheme 1.
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藤井 勲, 飯島 洋, 海老塚 豊, 三川 潮
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(+)Geodin (1), a seco-anthraquinone, is an antibiotic produced by fungi. Its biosynthesis has been studied by extensive feeding experiments and established as shown in Fig. 1. A variety of reactions involved in the biosynthsis of (+)geodin (1) drew our attention and we have studied the purification and characterization of the enzymes for (+)geodin (1) biosynthesis in Aspergillus terreus IMI 16043. i) Emodinanthrone oxygenase was detected in cell free system and analyses of the enzymically formed emodin (3) by MS and ^<13>C-NMR confirmed the incorporation of molecular oxygen into corresponding site of emodin (3). ii) Emodin O-methyltransferase, an enzyme catalyzing methylation of emodin (3) to produce questin (4), was purified up to 89 fold by Blue Sepharose and Sepharose 6B. This enzyme was found to have low Km value and high specificity for emodin (3). iii) Questin oxygenase system, which converts questin (4) into benzophenone, desmethylsulochrin (5) by a Baeyer-Villiger type oxidation, was observed in soluble fraction, and fractionated into two activities, an unstable oxygenase and possibly an NADPH oxidase. iv) Final step of (+)geodin (1) biosynthesis is phenol oxidative coupling reaction catalyzed by Dihydrogeodin oxidase. The purified oxidase exhibited characteristics of blue copper protein and the presence of copper was confirmed by atomic absorption analysis. Dihydrogeodin oxidase is the first phenol oxidative coupling enzyme specific for natural product biosynthesis which has been purified and characterized.
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佐藤 良博, 小田 泰子
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The stereochemistry of microbial transformation of the titled compounds was elucidated by 400MHz PMR and 41.41 MHz ^2H-NMR and by CD spectral data. Streptomyces cinereocrocatus was used as a micro-organismus with the intention of comparing the results with those obtained previously on (-)- and (+)-dehydrogriseofulvin and their analogs (Chart 1). (+)- and (-)-2'-Demethoxydehydrogriseofulvin (5 and 6) synthesized as substrates were subjected to the microbial transformation by S. cinereocrocatus. The transformation of (-)-enantiomer afforded (+)-2'-demethoxy-2',3'-dihydrodehydrogriseofulvin (16) as a sole product in 60% yield. On the other hand, the microbial transformation of (+)-enantiomer gave (+)-2'-demethoxygriseofulvin and a mixture of (-)- and (+)-2'-demethoxy-2',3'-dihydrodehydrogriseofulvin (13 and 16) in 12 and 8% yields, respectively. The results indicate that the microbial transformations take place directly and/or after isomerization with hydrogenation depending on (+)- or (-)-2'-demethoxydehydrogriseofulvin (Chart 4). In order to elucidate the stereochemistry of the microbial hydrogenation, deuterated substrates (5a,5b, 6a and 6b) were subjected to the same microbial transformation as performed in undeuterated substrates, and undeuterated stubstrates, on the other hand, were transformed in a medium containing deuterium oxide. PMR and ^2H-NMR analyses (Fig. 2 and 3) of the deuterated products revealed that hydrogenations of the dienones proceed in transdiaxial manner to give the corresponding products in the results so far obtained (Chart 5 and 6).
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柿沼 勝己, 今村 信孝, 浦本 昌和, 鵜沢 洵
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A chirality transfer approach was developed for the preparation of chiral glycine which was supposed to be a key substrate for the stereochemical studies of the biosynthesis of unique 17-membered carbocyclic antibiotics lankacidins. This approach is comprised from conversion of acetylene (HC≡CH) into chiral glycine (H_2N-H-C-^2H-COOH) via: 1) addition of acetylene to a chiral ketone 2; 2) stereospecific ^2H introduction during the reduction of the acetylene 3 to olefins (e.g. 5); 3) epoxidation followed by introduction of a nitrogen functionality; and 4) oxidative cleavage of the resulting glycol (e.g. 8) and further oxidation to the desired chiral glycine derivatives (e.g. 10). Also described was a new access to chiral acetic acid from the above-mentioned epoxides (e.g. 6 and 7) by the use of stereospecific reduction with tritiated LiAlH_4 and oxidation. Simultaneous feeding of [1-^<13>C]- and [^2H_5]glycine to the fermentation of a lankacidin producing Streptomyces strain was undertaken to clarify the behavior of hydrogen atoms of glycine during the formation of its 17-membered carbocyclic system and no deuterium incorporation was observed into the H-3 position in contrast to apparent ^<13>C enrichment at the C-4 position. A mechanism suggested is the formation of an 18-membered carbocyclic intermediate prior to the ring contraction to the 17-membered ring probably via a Favorskii-type rearrangement analogous to the biosynthetic mechanism of polyketide δ-lactones such as an Aspergillus pyrone (aspyrone) and vulgamycin.
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松尾 昭彦, 湯木 俊次, 東 涼一, 中山 充, 林 修一
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In the course of our investigation on the terpenoids of the liverworts which contain several oil bodies in each cell of the gametophytes, we found that the liverworts produce the sesquiterpenoids enantiomeric with those in higher plants. From the leafy liverwort Herberta adunca (Dicks.) S. Gray we now isolated five sesquiterpenoids consisting of a novel carbon skeleton named herbertane. The structure including absolute configuration of these compounds naming (-)-herbertene (1), (-)-α-herbertenol (2), (-)-β-herbertenol (3), (-)-α-formylherbertenol (4) and (-)-herbertenediol (5) were determined by the chemical and spectral evidence. The results provide a further illustration of the tendency of liverworts to produce the sesquiterpenoids which are enantiomers of those isolated from higher plants. The natural phenols (2, 3 and 4) and the bromide (19) inhibit the growth of some pathogenic fungi causing plant disease.
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市原 耿民, 及川 英秋, 林 和子, 橋本 真明, 坂村 貞雄, 古崎 昭雄, 松本 毅
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Several phytotoxins which are active for leaf test of sugar beet and lettuce germination were isolated from culture filtrates of Phoma betae Fr, the incitant of leaf spot disease of sugar beet. Three of them were confirmed to be aphidicolin (1), aphidicolin-17-monoacetate (2), and 3-deoxyaphidicolin (3) on the bases of spectroscopic evidence and chemical correlations. The other two metabolites betaenone A (7) and betaenone B (8), are novel compounds and the structure of the former (7) has been determined by X-ray crystallographic analysis. The structure of betaenone B (8) were elucidated from spectroscopic data of 8 and its derivatives, and confirmed definitely by correlation of 8 with 7.
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石塚 みどり, 楠見 武徳, 柿澤 寛
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From the brown alga, Pachydictyon coriaceum, which was collected at the Izu-Shimoda beach, Japan, five new diterpenes, sanadaol (5), acetylsanadaol (6) acetyldictyolal (7), acetals (9a) and (9b), and acetyldictyol C (10), were isolated together with the known diterpenes, dictyolactone (1), dictyodial (2), dictyol E (3), and 18-hydroxy-2,7-dolabelladiene (4). The structures of the new diterpenes were elucidated by spectroscopic analyses and chemical conversions. Among the new diterpenes, 5 and 6 have the novel skeleton, which has not been found in natural products. Noteworthy is the fact that sanadaol (5) is formed in a considerable yield from dictyodial (2), when the latter was allowed to stand with silica gel in dichloromethane at room temperature. Possibly, an intramolecular ene reaction took place between the aldehyde (C-18) and the transannular olefin (C-6,7) groups. The detailed mechanism of this unusual cyclization is discussed. Acetyldictyolal (7) was converted into dictyolactone (1) by hydrolysis followed by oxidation (MnO_2/CH_2Cl_2). Also, acetyldictyol C(10) was transformed into known dictyol C (12) by hydrolysis at 65℃ (KOH/MeOH). When the acetals (9a,b) were hydrolyzed (SiO_2), dictyodial (2) was formed, besides 5. It is of interest that the present alga produces plenty of diterpenes composed of various kinds of skeletons.
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孫 漢董, 林 中文, 南 慶典, 丸中 照義, 藤多 哲朗, 武田 美雄
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During the course of our studies on the biologically active principles of Rabdosia plants, the constituents of three Rabdosia plants, R. phyllostachys (a), R. rubescens(b) and R. sculponeata(c), in China have been investigated. Five new diterpenoids, phyllostachysin A from (a), rubescensin D from (b), sculponeatins A, B and C from (c) were isolated. These compounds were elucidated to possess the structures 1, 11, 14, 16 and 18, respectively, on the basis of spectroscopic and chemical evidence.
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石橋 正己, 古野 哲郎, 直良 弘一, 廣田 洋, 村江 達士, 露木 孝彦, 高橋 武美, 板井 昭子, 飯高 洋一, 松下 和弘
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Bitter Principles isolated from Simaroubaceous plants have been extensively investigated. We recently examined constituents of the root and stem bark of Ailanthus altissima SWINGLE (Japanese name: Shinju or Niwaurushi) and isolated five new quassinoids. Shinjulactones A (5) and D (6) were shown to be quassinoids with normal picrasane skeleton (1), while shinjulactones B (7), C (8), and shinjudilactone (9) were those with new migrated picrasane skeletons. On heating with sodium hydrogencarbonate in aqueous methanol ailanthone (4) afforded shinjudilactone (9) and its 13-epimer (11) in a ratio of 1:1 in good yields by benzilic acid rearrangement.
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野副 重男, 小池 隆, 辻 恵美, 草野 源次郎, 瀬戸 治男, 青柳 富貴子, 松本 春樹, 松本 毅, 奥野 智旦
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セッションID: 38
発行日: 1982/09/10
公開日: 2017/08/18
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In the course of our continuing investigation of the constituents of a hallucinogenic mushroom, Gymnopilus spectabilis (Japanese name, O-waraitake) collected at Oguni, Yamagata, we have isolated novel type of polyisoprenepolyols designated as gymnopilins -A, -B, and gymnoprenols -A, -B, -C, and -D etc. These substances occured as a mixture of some homologues were separated and throughly purified by means of preparative HPLC and their chemical structures were determined on the basis of the results of oxidative degradation as well as their spectroscopic properties. These polyisoprenepolyols were shown to contain same repeated unit corresponding to hydrated form of usual isoprenoid chain, two or three double bonds and a terminal vicinal diol moiety or the corresponding ester with 3-hydroxy-3-methyl-glutaric acid. The location of double bond was confirmed by the degradation studies. The structures of polyisoprenepolyols such as 1a and 2a have never been encountered in natural products obtained so far. The stereochemistry and biological activities are under investigation.
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高津戸 秀, 池川 信夫, 安部 浩, 森下 忠志, 内山 正昭, 池田 道正, 佐々 武史, 丸茂 晋吾, 橘和 丘陽
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セッションID: 39
発行日: 1982/09/10
公開日: 2017/08/18
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We have established a microanalytical method for identification of brassinolide as the bismethaneboronate derivative by the computerized mass fragmentography using GC-CIMS system, which allow us to detect as small as picogram amount. The derivatives exhibit moderate volatility and strong molecular ions(e.g. m/z 529 for brassinolide; m/z 513 for the 6-keto analogue ) as base peaks in CI-MS as shown in Fig. 3 and methane boronic acid is a specific reagent for vicinal diol derivatization effecting easy separation from other contaminants in GC. The extracts from the immature seeds and sheaths of chinese cabbage, the leaves of green tea, and the insect galls of chestnut tree were first bioassayed by the rice-lamina inclination test, a highly specific and sensitive method for brassinosteroids and the biologically active fractions were derivatized and analyzed by this microanalytical technique. Brassinolide and its analogues(II, V, VII, VIII) were positively identified as shown in Fig. 4 and 5, thus indicating the ubiquitous distribution of brassinosteroids in the plant kingdom.
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高井 誠, 齋藤 保, 飯高 洋一
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セッションID: 40
発行日: 1982/09/10
公開日: 2017/08/18
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From the Chinese crude drug "Huanggi" (Astragali Radix, Leguminosae), four new triterpenoid glycosides astragaloside I(1), II(2), III(3), IV(4) were isolated. Their structures were elucidated by X-Ray crystallographic analysis of octamethyl-astragaloside IV(8) and spectroscopic data. The aglycone cycloastragenol (5) is 20R,24S-epoxy-9,19-cyclolanostn-3β,6α, 16β,25-tetraol. Astragaloside A-I(12), A-II(13), A-III(14), A-IV(15), A-V(16) were isolated from the aerial parts of Astragalus membranaceus Bunge., which roots are used for Astragali Radix. Their aglycones are 20-epi-cycloastragenol (18) and cycloastragalol (24) (9,19-cyclolanostan-3β,6α,16β,24ξ,25-pentaol) and 20-epi-6-keto-cyclo-astragenol (27). Astragaloside C-I(28), C-II(29), C-III(30), C-IV(31), C-V(32) were isolated from the aerial parts of Astragalus concretus Benth. which was collected in Nepal.
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宮原 一元, 工藤 恵子, 川崎 敏男
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セッションID: 41
発行日: 1982/09/10
公開日: 2017/08/18
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During a study on the constituents of fresh underground parts of Rhodea japonica, two spirostanol glycosides R-3(I) and R-8(II) were obtained. I and II seemed pure on normal- and RP-TLC, and characterized, respectively, as 1-O-rhamno-xyloside and 3-O-glucoside of rhodeasapogenin(5β-25S-spirostan-1β,3β-diol)(III). They were, however, acid hydrolyzed to yield III and minor amounts of isorhodeasapogenin(25R)(IV) and convallamarogenin(Δ^<25(27)>)(V) indicating their unhomogeneity. As a method of purity control of the glycosides in situ, the CMR spectra were found to be of use, but in order to develop a new means which requires much less sample and provides much finer separation, and which could be extended to a preparative scale, application of HPLC was studied. By the method using Radial Pak C_<18> and 90% MeOH, I and II were separated, respectively, to give a new compound(I_a, II_a), the glycoside of V and a mixture of the glycosides of III and IV. Subsequent separation of the last mixture was, in the long run, successfully achieved by using TSK LS-410 column and 90% MeOH at 0℃. I_a and II_a were identified as the first natural glycosides, of which aglycones are equally 22-epi(22β-O)(22S), 25S(eq-Me) congener of III, and their properties and formation from the corresponding furostanol glycosides are discussed. The above HPLC was applied also to "dioscin," crude neotokoronin and "digitonin."
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橘 和夫, 堺谷 政弘, 中西 香爾
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セッションID: 42
発行日: 1982/09/10
公開日: 2017/08/18
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The sole Pardachirus pavoninus emits ichthyotoxic secretion from defensive cells lined at bases of its fins when disturbed. The secretion falls under the category of ichthyocrinotoxins which is presumed to work for the hosts as repellent against predatory fishes. The major hemolytic factor has been separated from the P. pavoninus secretion and found to be a mixture of steroid mono-glycosides, which are closely related to one another in terms of the chemical structure. The glycosides are lethal to Japanese killyfish at the concentration below 10 μg/mL and have comparable hemolytic activities to a commercial saponin on rabbit blood cell. Six major ichthyotoxins were isolated and named pavoninins-1, -2, -3, -4, -5, and-6. Their structures were elucidated to be 3, 4, 6, 7, 9, and 10 respectively by means of intensive ^1H nmr analyses and other spectroscopic studies, chemical modification, degradation, and correlation to one another.
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上田 博之, 塩島 憲治, 増田 和夫, 井上 正敏, 石田 寿昌
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セッションID: 43
発行日: 1982/09/10
公開日: 2017/08/18
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From the dried whole plants of Lemmaphyllum microphyllum var. microphyllum and L. microphyllum var. obovatum (Polypodiaceae), α-onoceradiene (I), serratene (II) and onoceranoxide (III) were isolated, and their structures were established by spectroscopic and chemical methods. Colysanoxide (IV), an onoceroid having a novel carbon skelton, was isolated from the dried leaves of Colysis elliptica and C. pothifolia (together with I), and its structure was established by spectroscopic and chemical methods as well as by a X-ray diffraction method. IV was also proved to be found in C. wrightii, C. x shintenensis and C. x simplicifrons by GC-MS. The compounds I-IV could be very characteristic triterpenoids, because they belong to the onoceroid gruop, squalenoids formed by both end cyclization, having no hydroxyl group. They were obtained only from very limited Polypodiaceous ferns.
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西沢 麦夫, 西出 久哉, 林 雄二, Soleh Kosela
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セッションID: 44
発行日: 1982/09/10
公開日: 2017/08/18
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New triterpene glycosides named lansiosides A, B, and C are isolated from the peel of fruits of an Indonesian tropical plants, Lansium domesticum Jack v. duku (Meliaceae). Their structures and absolute configurations are established by spectral study and chemical derivation. The same aglycone methyl ester is obtained by the methanolysis of three lansiosides. This aglycone is a skeletally new triterpenoid of seco-onoceran type, which is proved by derivation to a known triterpene lansic acid. Lansioside A is a novel example of amino-sugar glycoside (N-acetyl-β-D-glucosamine) obtained from plant origin. Lansiosides B and C are corresponding β-D-glucoside and β-D-xyloside, respectively.
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