Three NMR structures of α-conotoxin MI, a potent antagonist of the nicotinic acetylcholine receptor, have been refined using molecular dynamics (MD) simulation with explicit water. Although the convergence of the NMR structures of α-conotoxin MI was not sufficient to provide detailed structural features, the average structures obtained from MD simulations converged to one conformation, providing structural characteristics. The resulting structure was also found to be consistent with the results of amide proton-exchange experiments. These results demonstrate that MD simulation with explicit solvent water is very useful in refining NMR structures.

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The interaction of diphenyltin(IV) with selected bioligands having a variety of model functional groups were investigated using the potentiometric technique. The hydrolysis constants of diphenyltin(IV) cation and the step-wise formation constants of the complexes formed in solution were calculated using the non linear least-squares program MINIQUAD-75. The participation of different ligand functional groups in binding to organotin is discussed. The concentration distribution of the various complex species was evaluated as a function of pH.

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To improve the in vitro and in vivo potency of our first low molecular weight GPIIb/IIIa antagonist 1 (TAK-029), a series of 2-[4-[2-(4-amidinobenzoylamino)-2-(substituted)acetyl]-3-(2-methoxy-2-oxoethyl)-2-oxopiperazinyl]acetic acids were synthesized through modification of the glycine moiety of 1 and evaluated for their ability to inhibit in vitro adenosine 5'-diphosphate (ADP)-induced platelet aggregation of guinea pig platelet rich plasma (PRP). Among the compounds examined, the (3S, 2S)-4-methoxyphenylalanine derivative 4h showed the most potent antagonistic activity with an IC₅₀ value of 13 nM. Dose-dependent inhibition of ex vivo platelet aggregation was achieved with oral administration of 4h (0.3-1.0 mg/kg) to guinea pigs. Complete inhibition was observed for up to 8 h, and 43% inhibition could still be observed 24 h after oral administration of 1.0 mg/kg. The long-lasting antiplatelet effect of 4h suggests that 4h would be suitable for once-a-day dosing. Structure-activity relationships (SAR) were examined in the series of the phenylalanine derivatives. An increase in the electron density around the 4-position of the phenyl ring of the phenylalanine moiety led to an increase in the antiplatelet activity, suggesting the existence of a hydrophobic and electrostatic interaction site in addition to the ionic binding sites in the GPIIb/IIIa.

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To improve the in vivo potency of the potent GPIIb/IIIa antagonist 2-[(3S)-4-[(2S)-2-(4-amidinobenzoylamino)-3-(4-methoxyphenyl)propanoyl]-3-(2-methoxy-2-oxoethyl)-2-oxopiperazinyl]acetic acid (4), the amidino group was converted to an oxadiazole ring, thiadiazole ring or substituted amidoxime group. These groups were expected to be metabolized to an amidino group in vivo. The compounds synthesized were evaluated for their potency to inhibit the ex vivo adenosine 5'-diphosphate (ADP)-induced aggregation of guinea pig platelets. Among the compounds examined, the methoxycarbonyloxyamidine 8a exhibited the most potent ex vivo inhibitory activity with a fast onset and prolonged duration of action after oral administration.

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A simple and rapid indirect potentiometric titration of sulphamethoxazole in the presence of trimethoprim contained in co-trimazole tablets is described. The method is based on the formation of a complex of sulphamethoxazole with a known excess of silver ions and the titration of unreacted silver ion potentiometrically using an inexpensive lab-made copper based mercury film electrode (CBMFE). The titration conditions have been optimized for the determination of 1.0-10.0 mg of sulphamethoxazole in pure and dosage forms. The precision and accuracy of the method have been assessed by the application of lack of fit test and other statistical methods. Overall mean recovery and relative standard deviations obtained were 99.88% and 1.32% (n=7) respectively. No interference was caused by other excipients present in pharmaceutical dosage forms. The application of this method for sulphamethoxazole assay in the presence of trimethoprim in tablets was validated by the comparison of results obtained by the proposed method with that of the British Pharmacopoeia (BP) method using F- and t-statistical tests of significance.

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Thirty three compounds were obtained from the bulbs of Urginea maritima (Liliaceae). The compounds were identified by means of fast atom bombardment mass spectrometry (FAB-MS), nuclear magnetic resonance (¹H-NMR), (¹³C-NMR), nuclear overhauser effects (NOE) and two dimensional (2D) NMR. Ten of them were new natural compounds. Nine were bufadienolides and only one was lignan in these compounds.

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Positively charged porphyrins bearing an acridine with various lengths of diamino alkyl linkage, 5-[4-[(6-chloro-2-methoxy-9-acridyl)aminoalkylaminocarbonyl]phenyl]-10, 15, 20-tris(4-N-methylpyridiniumyl)porphine triiodide, alkyl=ethyl, butyl, hexyl, or octyl, were synthesized. They exhibited more enhanced photocleavage activity of pUC18 plasmid DNA than TMPyP, meso-tetrakis(4-N-methylpyridiniumyl)porphine, which is well known to bind to DNA tightly and to cleave DNA effectively; the hybrid linked with the hexamethylene chain showed particularly high activity. An equilibrium dialysis experiment demonstrated that the binding ability of the hybrids to calf thymus (CT) DNA correlated quantitatively with the photocleavage activity. The lack of the substantial red-shift of the Soret maxima of the hybrids through the titration with CTDNA denied the intercalative binding of the porphyrin part. In their circular dichroism (CD) spectral change on binding to CTDNA, two negative peaks appeared at 275 nm and at 285-290 nm in the UV range. The latter negative peak was observed for hybrids, but not for TMPyP, and thus we assigned it to induced CD (ICD) derived from intercalation of acridine chromophore. In the visible range, the hybrids showed only a positive peak around their Soret maxima, and this feature suggested the porphyrin moiety lay in the DNA groove. In addition, the length of the linker markedly influenced the ellipticity of their visible ICD, suggesting that the proximity of the porphyrin moiety to DNA was greatly affected by the linker.

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Hydrogen peroxide (H₂O₂)-induced deacetylation of non-fluorescent acetyl resorufin (1) to fluorescent resorufin (2) as a novel indicator reaction for fluorometric detection of glucose using only glucose oxidase (GOD) is described. When a 1:1:1 mixture of 1 (in CH₃CN), glucose, and GOD (each in pH 7.4 phosphate buffer) was incubated at 25 °C under aerobic conditions, the resulting solution turned yellow to fluorescent pink due to 2. The formation of 2 was markedly retarded on incubation under anaerobic conditions. When a mixture of 1 and H₂O₂ was incubated under aerobic conditions, the formation of 2 was noted as in the case of the enzymatic reaction of 1. These results demonstrated that the observed color change is brought about through deacetylation of 1 to 2 induced by H₂O₂ generated in GOD-catalyzed oxidation of glucose. With regard to the fluorometric traces of the enzymatic reaction with 1 (0.2 mM), GOD (0.5 mg/ml), and glucose at 25 °C, fluorescence intensity exhibited a linear relationship against glucose concentration between 0.2 and 2.0 mM, with a correlation coefficient of 0.997. Neither ascorbic acid, uric acid, nor bilirubin significantly interfered with the transformation of 1 to 2 through GOD-catalyzed oxidation of glucose.

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The influence of various phenolic compounds on the lactoperoxidase (LPO)/hydrogen peroxide (H₂O₂)-catalyzed oxidation of biochemical reductants such as reduced β-nicotinamide adenine dinucleotide (NADH), reduced β-nicotinamide adenine dinucleotide phosphate (NADPH) or reduced glutathione (GSH) was investigated by electron spin resonance (ESR) spectroscopy. Micromolar quantities of phenolic compounds such as 17β-estradiol, phenol, and p-chlorophenol enhanced the LPO/H₂O₂-catalyzed oxidation of NAD(P)H or GSH to generate a large amount of superoxide radical (O₂^·-) or glutathione thiyl radical (GS^·), while, phenolic compounds such as quercetin and Trolox C greatly suppressed the generation of O₂^·- and GS^·. In order to elucidate the effects of phenolic compounds on the generation of O₂^·- and GS^·, their quenching activities for a stable radical, 1, 1-diphenyl-2-picrylhydrazyl (DPPH), were investigated by ESR spectroscopy. 17β-Estradiol, phenol, and p-chlorophenol showed very weak scavenging activities for DPPH, but quercetin and Trolox C showed strong activities. This suggests that the ability of phenolic compounds to enhance LPO/H₂O₂-catalyzed oxidation of NAD(P)H or GSH relates inversely to their ability to quench DPPH. That is, phenolic compounds having weak quenching activity against DPPH may enhance the LPO/H₂O₂-catalyzed oxidation of NAD(P)H or GSH to generate a large amount of O₂^·- or GS^·.

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The crystals of 1α, 24(R)dihydroxy-vitamin D₃ monohydrate, C₂₇O₃H₄₄·H₂O are orthorhombic in the space group P2₁2₁2₁ with cell dimensions a=25.719, b=42.572, c=9.851 Å and Z=16. The asymmetric unit consists of two subunits with b/8, and each subunit contains a dimer in which two molecules are hydrogen-bonded through water molecules into non-crystallographical symmetry of C₂. The two-fold axes are the straight lines, x=1/2, z=0.256 and x=1/2, z=0.623. The two dimers are the same in the rigid ring part, but differ in the conformation of the flexible chains. The dimers further make C₂ symmetry between the rigid ring parts to form a superstructure, and the two-fold axis of the straight line, y=1/8, z=0.435 goes through a point that is a little apart from the hypercenter (1/2, 1/8, 1/2). The structure was solved by integrated Patterson and direct methods and refined on F_o² under restraints. The final R₁ is 0.228 on F_o for 1623 reflections with F_o>3σ, resolutions 1.0-3.0 Å, 313 restraints, 490 parameters and average U_eq=0.120. Not all the atoms of the chains appeared nor the hydrogen atoms. The missing atoms of the dimer were modeled from another pair molecule by C₂ symmetry and hydrogen atoms were added. The structure of the dimer was optimized by ab initio molecular orbital of HF/6-31G^*.

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An efficient synthetic route to (10Z)- and (10E)-19-fluoro-1α, 25-dihydroxyvitamin D₃ was developed. The key feature of this pathway is the introduction of a 19-fluoromethylene group to a (5E)-19-nor-10-oxo-vitamin D derivative. The 10-oxo-compound was obtained via a 1, 3-dipolar cycloaddition reaction of (5E)-1α, 25-dihydroxyvitamin D with in situ generated nitrile oxide followed by ring cleavage of the formed isoxazoline moiety with molybdenum hexacarbonyl. Conversion of the keto group of (5E)-19-nor-10-oxo-vitamin D to the E and Z fluoromethylene group was achieved through a two-step sequence involving a reaction of lithiofluoromethyl phenyl sulfone followed by the reductive desulfonylation of the α-fluoro-β-hydroxy sulfone. The dye-sensitized photoisomerization of the (5E)-19-fluorovitamin D afforded the desired (5Z)-19-fluorovitamin D derivatives, (10Z)- and (10E)-19-fluoro-1α, 25-dihydroxyvitamin D₃.

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Two steroidal saponins, hemeroside A and B, were isolated from the aerial part of Hemerocallis fulva var. kwanso for the first time. The structures of these compounds were established as 24S-hydroxy-neotokorogenin 1-O-α-L-arabinopyranosyl 24-O-β-D-glucopyranoside (1) and isorhodeasapogenin 3-O-β-D-glucopyranosyl-(1→3)-[β-D-xylopyranosyl-(1→2)]-β-D-glucopyranosyl-(1→4)-β-D-galactopyranoside (2) through NMR experiments.

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A mixture of cerebrosides, called poke-weed cerebrosides, was purified from Phytolaccae Radix (Phytolaccaceae) and characterized as 1-O-β-D-glucopyranosides of phytosphingosine type ceramides comprised of a common long chain base (2S, 3S, 4R, 8Z)-2-amino-8-octadecene-1, 3, 4-triol and fatty acids. The fatty acyl chain of ceramide moieties was determined as (2R)-2-hydroxypentacosanoic acid, (2R)-2-hydroxylignoceric acid, (2R)-2-hydroxytricosanoic acid, (2R)-2-hydroxybehenic acid, (2R)-2-hydroxypalmitic acid, and palmitic acid. The poke-weed cerebroside inhibited the cyclooxygenase-2 dependent phase of prostaglandin D₂ generation in bone marrow-derived mast cells in a concentration dependent manner with an IC₅₀ of 6.2 μg/ml.

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Electrocatalytic oxidation of N-alkyl-N-methylanilines was studied using 4-benzoyloxy-2, 2, 6, 6-tetramethylpiperidinyl-N-oxyl as a nitroxyl radical. The reaction with N-alkyl-N-methylanilines led to direct formation of N-alkylformanilides in the presence of H₂O in reaction media in adequate conversion (>75.8%), high current efficiency (>89.2%) and high selectivity (>93.8%).

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A new benzofuran glycoside, masutakeside I (1) and a new C₁₀ acetylenic acid, masutakic acid A (2) were isolated from the fruiting bodies of the fungus Laetiporus sulphureus var. miniatus. Their structures were established by spectroscopic and chemical methods. The known compounds 3-6 were also obtained and identified as egonol, demethoxyegonol, egonol glucoside and egonol gentiobioside. Some of these compounds exhibited cytotoxicity against Kato III cells.

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Based on the solution structures of chiral bidentate lithium amides ((R)-3a, b) having a phenyl group on the chiral carbon, chiral bidentate amines ((R)-5a, b-8a, b and (S)-9a, b) having a bulkier group instead of a phenyl group on the chiral carbon were designed and synthesized.

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N-Substituted 2-acetylamino-2-ethoxycarbonyl-3-(2-furyl)propanamides (8) were synthesized through the reaction of amines (13) with 2-acetylamino-2-ethoxycarbonyl-3-(2-furyl)propanoic acid (3b), which was prepared via condensation of 2-(bromomethyl)furan (10b) with diethyl acetamidomalonate, followed by partial hydrolysis of the resultant diethyl ester (3a) in the presence of barium hydroxide. However, bulky amines such as tert-butyl-amine or 2-trifluoromethylaniline did not afford the corresponding diamides (8). The biological activity of the prepared diamides (8) as root growth modulators was examined by germination assay using rape and leek seeds. N-(5-Bromo-2-thiazolyl)- and N-(4-chloro-2-benzothiazolyl)-2-acetylamino-2-ethoxycarbonyl-3-(2-furyl)propanamides (8h, i) both potently inhibited the root growth of rape seedlings, but were less effective in the case of leek seeds. The herbicide 2, 4-dichlorophenoxyacetic acid completely inhibited root growth in both cases.

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We describe the practical synthetic route for (2S)-7-methoxy-1, 2, 3, 4-tetrahydro-2-naphthylamine [(2S)-2-amino-7-methoxytetraline; (S)-AMT]. (2R)-2-(3-Methoxybenzyl)succinic acid [(R)-1] was obtained by the optical resolution of 2-(3-methoxybenzyl)succinic acid (1) as the salt of (1R, 2S)-2-(benzylamino)cyclohexylmethanol (7), and (R)-1 was converted to the optically active (2S)-7-methoxy-1, 2, 3, 4-tetrahydro-2-naphthoic acid [(S)-2] by the intramolecular Friedel-Crafts reaction followed by catalytic hydrogenation. (S)-AMT was obtained from the acid (S)-2 by Hofmann rearrangement without racemization.

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The iron(II) complex of 2, 7, 12, 17-tetraethyl-3, 6, 11, 18-tetramethylcorrphycene, an isomeric heme, was complexed with apomyoglobin to examine the ligand binding ability of the novel macrocycle under physiological conditions. The reconstituted holoprotein was found to be functionally active at pH 7.4 and 20 °C and to bind oxygen and carbon monoxide reversibly with a half-saturation pressure at 6.7 and 3.5 mmHg, respectively. Equilibrium affinities for these ligands are one to two orders of magnitude lower than those reported for native myoglobin. The functional anomaly was ascribed to the geometric and electronic strain on the iron(II) atom in the trapezoidal coordination core of corrphycene.

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