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Volume 55, Issue 12
Displaying 1-24 of 24 articles from this issue
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Regular Articles
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Wieslawa Misiuk, Agnieszka Tykocka2007 Volume 55 Issue 12 Pages 1655-1661
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSTwo simple, sensitive and rapid extractive spectrophotometric methods have been developed for the assay of the antidepressant drug nortriptyline (NOR) hydrochloride in pure form and in different dosage forms. The methods involve the formation of colored ion-pairs between the drug and the complex of niobium(V)-thiocyanate (Nb-SCN) or iron(III)-thiocyanate (Fe-SCN) followed by their extraction with butanol or a mixture of butanol and chloroform and quantitative determination at 360 nm and 490 nm, using Nb-SCN and Fe-SCN, respectively. The experimental conditions were optimized to obtain the maximum colour intensity. The methods permit the determination of nortriptyline over a concentration range of 15—100 μg/ml and 5—24 μg/ml with the detection limit of 0.84 μg/ml and 0.32 μg/ml, using Nb-SCN and Fe-SCN, respectively. The proposed methods are applicable for the assay of the investigated drug in different dosage forms and the results are in good agreement with those obtained by the official and HPLC methods. No interference was observed from common excipients present in pharmaceutical formulations. The proposed procedures were applied to determine the amount of nortriptyline hydrochloride as active ingredient in the presence of its degradation product, dibenzosuberone. The extractive spectrophotometric methods can also be used to determine the amount of nortriptyline hydrochloride in tablets after its solid phase extraction (SPE).View full abstractDownload PDF (92K) -
Nahed El-Enany, Dina El-Sherbiny, Fathalla Belal2007 Volume 55 Issue 12 Pages 1662-1670
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSFour sensitive, simple and specific methods were developed for the determination of desloratadine (DSL), a new antihistaminic drug in pharmaceutical preparations and biological fluids. Methods I and II are based on coupling DSL with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) in borate buffer of pH 7.6 where a yellow colored reaction product was obtained and measured spectrophotometrically at 485 nm (Method I). The same product could be measured spectrofluorometrically at 538 nm after excitation at 480 nm (Method II). Methods III and IV, on the other hand, involved derivatization of DSL with 2,4-dinitrofluorobenzene (DNFB) in borate buffer of pH 9.0 producing a yellow colored product that absorbs maximally at 375 nm (Method III). The same derivative was determined after separation adopting HPLC (Method IV). The separation was performed on a column packed with cyanopropyl bonded stationary phase equilibrated with a mobile phase composed of acetonitrile–water (60 : 40, v/v) at a flow rate of 1.0 ml min−1 with UV detection at 375 nm. The calibration curves were linear over the concentration ranges of 0.5—6, 0.02—0.4, 1—10 and 1—30 μg ml−1 for Methods I, II, III and IV, respectively. The lower detection limits (LOD) were 0.112, 0.004, 0.172 and 0.290 μg ml−1, respectively, for the four methods. The limits of quantification (LOQ) were 0.340, 0.012, 0.522 and 0.890 μg ml−1 for Methods I, II, III and IV, respectively. The proposed methods were applied to the determination of desloratadine in its tablets and the results were in agreement with those obtained using a reference method. Furthermore, the spectrofluorometric method (Method II) was extended to the in-vitro determination of the drug in spiked human plasma, with a mean percentage recovery (n=4) of 99.7±3.54. Interference arising from endogenous amino acids has been overcome using solid phase extraction. The proposed methods are highly specific for determination of DSL in the presence of the parent drug loratadine. A proposal for the reaction pathways is postulated.View full abstractDownload PDF (186K) -
Hisanaka Ito, Junya Iwasaki, Yuki Sato, Miwako Aoyagi, Kazuo Iguchi, T ...2007 Volume 55 Issue 12 Pages 1671-1676
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSFive new briarane-type diterpenoids, pachyclavulides E (5), F (6), G (7), H (8) and I (9), were isolated from the Okinawan soft coral Pachyclavularia violacea. The structures of these compounds were elucidated based on the results of spectroscopic analysis. Compound 5 showed a weak growth-inhibitory activity in vitro toward cancer cells.View full abstractDownload PDF (272K) -
Xiao-Yan Tian, Ying-Hong Wang, Hong-Yue Liu, Shi-Shan Yu, Wei-Shuo Fan ...2007 Volume 55 Issue 12 Pages 1677-1681
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSBioassay-guided fractionation of 95% EtOH extract from the roots of Dipsacus asper lead to the isolation of some phenolic acids (caffeic acid, 2,6-dihydroxycinnamic acid, vanillic acid, 2′-O-caffeoyl-D-glucopyranoside ester, and caffeoylquinic acid) as the major active components, and five new iridoid glucoside dimers (1—5) and one new iridoid glucoside monomer (6), other known iridoid glycosides loganin, cantleyoside, triplostoside A, lisianthioside, 6′-O-β-D-apiofuranosyl sweroside, as well as triterpenoids oleanic acid and akebiasaponin D. The structures of new compounds 1—6 were determined as dipsanosides C (1), D (2), E (3), F (4), G (5), and 3′-O-β-D-glucopyranosyl sweroside (6) by spectroscopic, including 1D and 2D NMR techniques, and chemical methods.View full abstractDownload PDF (102K) -
Norimasa Kanamitsu, Takashi Osaki, Yutaka Itsuji, Masakazu Yoshimura, ...2007 Volume 55 Issue 12 Pages 1682-1688
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSWe developed new intravenous sedative-hypnotic compounds with the isoindolin-1-one skeleton focusing on the water-soluble property and in vivo safety. We synthesized approximately 170 derivatives and evaluated their hypnotic effects by intravenous administration of the compounds to mice. A series of the 2-phenyl-3-[2-(4-methyl-1-piperazinyl)-2-oxoethyl]isoindolin-1-one analogs, 3(−), 5(−), 27(−), and 47(−) [JM-1232(−)], showed potent sedative-hypnotic activity with good water solubility and a wide safety margin. The hypnotic doses (HD50s) of these 4 compounds when administered to mice were 2.35, 1.90, 2.17, and 3.12 mg/kg, respectively, and the lethal doses (LD50s) were 88.67, 64.69, >120, and >120 mg/kg, respectively. The therapeutic indexes (LD50/HD50) were 37.73, 34.05, >55.30, and >38.46, respectively. Among these compound, 47(−) [JM-1232(−)] is being considered as the most potential candidate for clinical trials in humans.View full abstractDownload PDF (196K) -
Predrag Djurdjević, Ljubinka Joksović, Ratomir Jelić, A ...2007 Volume 55 Issue 12 Pages 1689-1699
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSComplex formation between aluminum(III) ion and fluoroquinolone antibacterials-either moxifloxacin (4th generation antibiotic) or fleroxacin (2nd generation antibiotic) were studied in aqueous solutions without and in the presence of sodium dodecylsulfate (SDS). The investigations were performed by glass electrode potentiometric (ionic medium: 0.1 mol/dm3 LiCl, 298 K), UV spectrophotometric, multinuclear (1H and 13C) magnetic resonance and ESI-MS measurements. The experimental data were consistent with the formation of Al(HL)L2+, Al(HL)3+, AlL2+, Al(OH)L+ and Al(OH)2L complexes in the pH interval ca. 3—8 and up to 5 : 1 ligand to metal mole ratio with range of Al3+ concentrations between ca. 0.025 to 1.0 mmol/dm3. The binary complex, AlL2+ is fairly stable (log β1,0,1 ca. 11.0) and its stability increases in the presence of SDS. At higher concentration ratios of ligands to aluminum, up to 5 : 1, the complex Al(HL)L2+ is formed with rather high overall stability constant (log β1,1,2 ca. 24.0). The ESI-MS data generally, confirmed the derived model, and the formation of the complex with ligand to metal ratio 2 : 1. NMR measurements indicate that both ligands utilize 4-carbonyl and carboxyl oxygens as donor atoms. The presence of surface active substance, SDS, favors the formation of the complex in which the ligand is protonated, i.e. Al(HL) and its maximum formation is shifted toward milder acidic region (pH ca. 4). The aluminum–quinolone complexes may affect the bio-distribution of both, quinolone and/or aluminum ion upon concomitant ingestion of aluminum-based antacids or phosphate binders and fluoroquinolones.View full abstractDownload PDF (509K) -
Hiroharu Kato, Tomohiro Kino, Fumihiko Yamamoto, Tetsuo Kaneshiro, Tak ...2007 Volume 55 Issue 12 Pages 1700-1703
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSAs part of our program to develop potential imaging agents for ascorbate bioactivity in the brain, 5-O-(4′-iodobenzyl)-L-ascorbic acid was prepared through a seven-step sequence which involved C5-O-alkylation with p-iodobenzyl bromide in the presence of Ag2O and CaSO4 as the key step, starting from L-ascorbic acid. The scavenging activity of the p-iodobenzylated analog against 2,2-diphenyl-1-picrylhyrazyl (DPPH) radical was almost the same as that of L-ascorbic acid itself.View full abstractDownload PDF (113K) -
Venkatapuram Padmavathi, Dandu Rangayapalle Chinna Venkata Subbaiah, K ...2007 Volume 55 Issue 12 Pages 1704-1709
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSNovel amino-pyrazolone, amino-isoxazolone and amino-pyrimidinone derivatives were prepared from ethyl 4-phenylsulfonyl-2-(2′-phenylsulfonylethyl)-2-cyanobutyrate (1), ethyl 4-arylsulfonyl-3-aryl-2-cyanobutyrate (7) and ethyl 4-arylmethylsulfonyl-3-aryl-2-cyanobutyrate (8). The lead molecules have been tested for their antimicrobial activity and antioxidant property.View full abstractDownload PDF (166K) -
Takashi Nagamine, Kohei Inomata, Yasuyuki Endo2007 Volume 55 Issue 12 Pages 1710-1712
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSThe enantioselectivity of the intramolecular asymmetric aldol reaction of 1,3-cycloheptanedione bearing a C-2 methyl substituent, mediated by a series of combinations of L-amino acid and Brønsted acid, was examined in detail.View full abstractDownload PDF (92K) -
Adi Issam Arida, Moawia Mohammed Al-Tabakha, Hantash Abdel Jalil Hamou ...2007 Volume 55 Issue 12 Pages 1713-1719
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSTo enhance the dissolution and oral absorption of poorly water-soluble griseofulvin (GF), self-emulsifying drug delivery system (SEDDS) composed of oil, surfactant and cosurfactant for oral administration of griseofulvin was formulated, and its physicochemical properties and pharmacokinetic parameters were evaluated. The solubility of griseofulvin was further improved by the addition of hydrochloric acid. Droplet size of griseofulvin emulsion was kept constant both in simulated gastric fluid without pepsin and simulated intestinal fluid throughout 12 weeks incubation period. Griseofulvin in the SEDDS rapidly dissolved in different dissolution media. This was not the case for the commercial GRIS-PEG® tablets. In different fed diet groups, AUC0→24 h, Cpmax, and Tmax of griseofulvin after oral administration of SEDDS in rats were comparable to those after oral dose of GRIS-PEG® tablet. Although, in fed lipidic diet group, the mean AUC and Cpmax after oral administration of GRIS-PEG® in rats were 1.28 and 1.15 fold higher, respectively, compared with those of SEDDS, these have not shown to be significantly different. These results demonstrate that the SEDDS of griseofulvin composed of Capmul® GMO-50, Poloxamer and Myvacet 9-45 greatly enhanced the dissolution of griseofulvin (without ultramicronisation). However, food intake effect on the bioavailability of griseofulvin has remained. Thus, this system may provide a useful dosage form for oral water-insoluble drugs which have problems in their dissolution.View full abstractDownload PDF (243K) -
Chih-Hua Chao, Ho-Cheng Huang, Yang-Chang Wu, Chung-Kuang Lu, Chang-Fe ...2007 Volume 55 Issue 12 Pages 1720-1723
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSThree glycolipids (1—3), possessing a sugar moiety at C-2 of glycerol ether, have been isolated from the Formosan soft coral Lobophytum crassum. Their structures were elucidated by spectroscopic methods, particularly in 1D- and 2D-NMR experiments. The absolute configurations on the sugar portion and lipid aglycon of 1—3 were determined by methanolysis, chemical transformation and the application of Mosher's method on 1 and 3. Compounds 1—3 exhibited weak cytotoxic activities.View full abstractDownload PDF (131K) -
Keiko Okimura, Kazuhiro Ohki, Yuki Sato, Kuniharu Ohnishi, Naoki Sakur ...2007 Volume 55 Issue 12 Pages 1724-1730
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSImproved strategies for the chemical conversion of natural polymyxin B and colistin to their N-terminal analogs are reported. First, the protection of the side chains of five L-α,γ-diaminobutyric acid (Dab) residues in natural polymyxin B and colistin was achieved with trichloroethoxycarbonyl (Troc), then the resulting pentakis(Nγ-Troc)-polymyxin B and pentakis(Nγ-Troc)-colistin were treated with trifluoroacetic acid (TFA) : methanesulfonic acid (MSA) : dimethylformamide (DMF) : H2O (10 : 30 : 55 : 5) at 40 °C in order to remove Nα-alkanoyl-Dab(Troc)-OH selectively. The new key compounds, tetrakis(Nγ-Troc)-polymyxin B (2-10) and tetrakis(Nγ-Troc)-colistin (2-10), were obtained in 19% and 15% yields, respectively, which is higher than previous reports using trifluoroacetyl (Tfa) for tetrakis(Nγ-Tfa)-polymyxin B (2-10) and tetrakis(Nγ-Tfa)-colistin (2-10), respectively. Acylation of tetrakis(Nγ-Troc)-polymyxin B (2-10) and tetrakis(Nγ-Troc)-colistin (2-10) with various hydrophobic acids bearing aliphatic or aromatic ring structures, followed by the deprotection of Troc by Zn in AcOH, produced polymyxin B (2-10) and colistin (2-10) analogs which were used for structure–activity relationship studies. It was found that cyclohexylbutanoyl-, 4-biphenylacetyl-, and 1-adamantaneacetyl-polymyxin B (2-10) showed potent antimicrobial activity equal to that of polymyxin B against three Gram-negative bacterial strains. The lipopolysacharide (LPS) binding activity of cyclohexylbutanoyl-, 4-biphenylacetyl-, and cyclododecanecarbonyl-polymyxin B (2-10) increased greatly in comparison with that of polymyxin B (2-10). The various Nα-acylated polymyxin B (2-10) analogs showed slightly higher antimicrobial and LPS binding activities than the corresponding Nα-acylated colistin (2-10) analogs.View full abstractDownload PDF (261K) -
Yohei Takahashi, Mika Yamada, Takaaki Kubota, Jane Fromont, Jun'ichi K ...2007 Volume 55 Issue 12 Pages 1731-1733
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSThree new sesquiterpenoids, metachromins R—T (1—3), have been isolated from an Okinawan marine sponge Spongia sp. The structures and stereochemistry of 1—3 were elucidated on the basis of the spectroscopic data. Metachromins S (2) and T (3) showed modest cytotoxicity.View full abstractDownload PDF (140K)
Notes
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Seong-Cheol Bang, Hyun-Hee Seo, Hwi-Yeol Yun, Sang-Hun Jung2007 Volume 55 Issue 12 Pages 1734-1739
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSA trisaccharide found in triterpenoid saponins isolated from Pullsatilla roots appears as an important promoiety for the enhancement of anticancer activity of their aglycones. Thus a facile synthetic method for a trisaccharide moiety, allyl-2,3,4-tri-O-benzoyl-α-L-rhamnopyranosyl-(1→2)-[2,3,4,6-tetra-O-benzoyl-β-D-glucopyranosyl-(1→4)]-3-O-benzoyl-β-L-arabinopyranoside (3), has been firstly developed through the regio- and stereoselective glycosylations from arabinose in total 16% yield via route 2 (eight steps). In this synthetic procedure, the protection of anomeric –OH of L-arabinose with equatorially oriented allyl group unlike with the axial 4-methoxybenzyl protecting group well promoted glycosyl bond formation between α-L-rhamnopyranosyl trichloroacetimidate and 2-OH of arabinose. As expected, the synthesized trisaccharide moiety 3 has no cytotoxicity (ED50: >100 μM) against three human cancer cell lines (A-549, SK-OV-3, and SK-MEL-2), respectively.View full abstractDownload PDF (267K) -
Chih-Chia Chiang, Jean-François Mouscadet, Hou-Jen Tsai, Chi-Ts ...2007 Volume 55 Issue 12 Pages 1740-1743
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSPresent studies were undertaken on the preparation of synthetic analogues of bis- or tetra-coumarins and their activity against HIV-1 integrase (HIV-1 IN). Among these coumarin analogues, compounds 14, 16 and 18 were found to be potent molecules against HIV-1 IN at IC50 values of 0.96, 0.58, and 0.49 μM, respectively. The results provided a tool for guiding the further design of more potent antiviral agents and for predicting the affinity of related compounds.View full abstractDownload PDF (158K) -
Hong-Wei Yu, Bo-Gang Li, Guo-You Li, Chang-Song Li, Dong-Mei Fang, Guo ...2007 Volume 55 Issue 12 Pages 1744-1747
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSTwo new abietane diterpene lactones (1—2), three new abietane diterpene lactone glycosides (3—5) and a new iridoid glycoside (6), together with five known compounds, were isolated from the aerial parts of Goldfussia yunnanensis. The new compounds were determined to be 18-hydroxyhelioscopinolide A (1), 18-oxohelioscopinolide A (2), 18-hydroxy-3-O-β-D-glucopyranosylhelioscopinolide A (3), 3-O-β-D-glucopyranosylhelioscopinolide A (4), 3-O-β-D-galactopyranosylhelioscopinolide A (5), and 6-O-trans-cinnamoyl E-harpagoside (6) on the basis of spectral data and chemical evidence.View full abstractDownload PDF (111K) -
Tatsuya Hasegawa, Mayumi Ishibashi, Takanobu Takata, Fumihide Takano, ...2007 Volume 55 Issue 12 Pages 1748-1749
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSThe new conjugated ketonic fatty acid, porrigenic acid (1), was isolated as a cytotoxic constituent of Pleurocybella porrigens. The structure of 1 was elucidated using spectroscopic methods including 1D and 2D NMR and MS. The absolute stereochemistry of 1 was determined by application of the exciton chirality method. Compound 1 exhibited cytotoxic activity against myeloma THP-1 cells, but did not show any significant toxicity against B16F1 melanoma. This is the first report of the isolation and structural elucidation of the new cytotoxic constituent porrigenic acid (1) from the edible mushroom P. porrigens.View full abstractDownload PDF (78K) -
Tomomi Noguchi-Yachide, Hiroyuki Miyachi, Hiroshi Aoyama, Atsushi Aoya ...2007 Volume 55 Issue 12 Pages 1750-1754
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSFollowing our previous discovery of LXR antagonistic activity of 2′-substituted phenylphthalimides derived from thalidomide-related glucosidase inhibitors, structure–activity studies and further structural development led to 5-chloro-N-2′-n-pentylphenyl-1,3-dithiophthalimide (5CPPSS-50), with IC50 values of about 10 and 13 μM for LXRα and LXRβ, respectively.View full abstractDownload PDF (423K) -
Hui Xu, Kun-Zhong Jian, Qiu Guan, Fei Ye, Min Lv2007 Volume 55 Issue 12 Pages 1755-1757
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSSeveral diaryl ethers were synthesized and tested in vitro against seven phytopathogenic fungi, namely Fusarium graminearum, Alternaria alternate, Helminthosporium sorokinianum, Pyricularia oryzae, Fusarium oxysporum f. sp. vasinfectum, Fusarium oxysporum f. sp. cucumarinum and Alternaria brassicae. Compared to a commercial agricultural fungicide, hymexazol, especially compounds a, b, e, g and k were found to be more effective at 50 μg/ml against F. graminearum, F. oxysporum f. sp. vasinfectum and F. oxysporum f. sp. cucumarinum. Meantime, some structure–activity relationships were also observed.View full abstractDownload PDF (256K) -
Michio Kurosu, Seiji Katayama, Hirotaka Shibuya, Isao Kitagawa2007 Volume 55 Issue 12 Pages 1758-1761
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSIn order to study calcium ion complex of soya-cerebroside II (1), an ionophoretic glucosylceramide isolated from soybean, C8-cerebroside (3) and 3,3″,6″-trideoxy-C8-cerebroside (4) are designed and synthesized. On the basis of extensive 1H-NMR studies in the presence of Ca2+ and a continuous variation method via 1H-NMR, soya-cerebroside II is suggested to form a calcium complex with 1/Ca2+ ratio of 1 : 1. Soya-cerebroside II serves as a tridentate chelating ligand for Ca2+; the amide carbonyl, C2′-hydroxy, and C2″-hydroxy oxygens are responsible for the Ca2+ binding. Soya-cerebroside II is structurally analogous to a neural glucosylceramide. Thus, the accumulated neural glucosylceramide inside of endoplasmic reticulum (ER) membrane may serve as an endogenous Ca2+-binding and -transport molecule (ionophore) that result in mobilization of Ca2+ from intracellular calcium stores.View full abstractDownload PDF (352K) -
Hideaki Sasaki2007 Volume 55 Issue 12 Pages 1762-1767
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSTwo new bithiazole derivatives, 2,2′-bis(3,6,9-triazanonyl)- and 2,2′-bis(3,7,11-triazaundecyl)-4,4′-bithiazoles (3a, b), were readily synthesized in six steps using the corresponding dialkylenetriamine as starting materials. Under physiological conditions, 5.0 μM 3a exhibited significant DNA cleavage activity in the presence of Co(II), whereas even at 50 μM, 3b exhibited no DNA cleavage activity. Furthermore, it was demonstrated that 3a forms a 1 : 2 complex with Co(II) ions, whereas 3b does not. These conclusions were based on measurements of stoichiometries of the bithiazole–cobalt complexes obtained by the Job continuous variation method. In contrast, 3a, which contains diethylenetriamine moieties, showed decreased affinity for Calf Thymus (CT) DNA compared with that of 3b, which contains dipropylenetriamine moieties. These findings indicate that the structure of the two aminoalkyl side chains attached at the 2- and 2′-positions of the 4,4′-bithiazole ring significantly influence the formation of cobalt complexes, and affects the compound's ability to cleave DNA as well as its affinity for double-stranded DNA.View full abstractDownload PDF (277K) -
Rie Kusano, Takashi Tanaka, Yosuke Matsuo, Isao Kouno2007 Volume 55 Issue 12 Pages 1768-1772
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSDuring black tea production, catechins and their galloyl esters are enzymatically oxidized to generate a complex mixture of black tea polyphenols. The role of galloyl ester groups in this process has yet to be determined. Enzymatic oxidation of epicatechin 3-O-gallate (1) yielded two new oxidation products, theaflavate C and bistheaflavate A, along with theaflavate A (2), a known dimer of 1 generated by coupling of the B-ring with the galloyl group. Theaflavate C is a trimer of 1 and possesses two benzotropolone moieties generated by the oxidative coupling of the galloyl groups with the catechol B-rings. Bistheaflavate A was found to be a tetramer produced by intermolecular coupling of two benzotropolone moieties of 2. From the structures of the products, it was deduced that oxidative coupling of galloyl groups resulted in extension of the molecular size of the products in catechin oxidation.View full abstractDownload PDF (134K) -
Kazuhiko Hayashi, Eiko Kujime, Hajime Katayama, Shigeki Sano, Yoshimit ...2007 Volume 55 Issue 12 Pages 1773-1775
Published: December 01, 2007
Released on J-STAGE: December 01, 2007
JOURNAL FREE ACCESSIn the imine aldol reactions of 1 with aromatic aldehydes using magnesium salts in the presence of amines, the threo/erythro ratios of products increased in the order Mg(ClO4)2>MgI2>MgBr2>MgCl2>Mg(OTf)2 and N,N,N′,N′-tetramethylethylenediamine (TMEDA)>Et3N. This increase in the threo/erythro ratios of products was estimated to be caused by a retro-imine aldol reaction under thermodynamic control.View full abstractDownload PDF (87K)
Errata
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2007 Volume 55 Issue 12 Pages 1776
Published: 2007
Released on J-STAGE: September 06, 2008
JOURNAL FREE ACCESSDownload PDF (64K)
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