Stereochemical Analysis of Trifluoroacetamide Derivatives Based on Through- HF Spin-Spin Couplings.

In this study, the conformational properties of tertiary trifluoroacetamides in dibenzoazepine ( and ) and benzodiazepine ( and ) derivatives, which exist as equilibrated - and amide conformers in solution, were investigated by H and F NMR spectroscopy. In all cases, one of the methylene protons neighboring the nitrogen atom of the minor conformer showed a finely split pattern due to coupling with the trifluoromethyl fluorine atoms, as confirmed by F-decoupling experiments. One-dimensional (1D) and two-dimensional (2D) H-F heteronuclear Overhauser spectroscopy (HOESY) experiments were performed to confirm whether these couplings are attributable to through- spin-spin couplings (TBCs) or through- spin-spin couplings (TSCs).

Conformational Preference of 2'-Fluoro-Substituted Acetophenone Derivatives Revealed by Through-Space H-F and C-F Spin-Spin Couplings.

The conformational properties of 2'-fluoro-substituted acetophenone derivatives were elucidated based on H-F and C-F through-space spin-spin couplings (TS-couplings), which occur between two atoms constrained at a distance smaller than the sum of their van der Waals radii. This study revealed that 2'-fluoro-substituted acetophenone derivatives in solutions form exclusively - conformers by analyzing their NMR spectra focused on the TS-couplings. The magnitudes of the coupling constants (H, F) and (C, F) correlate linearly with the value of the dielectric constant of the solvents.

Total Synthesis of Carthamin, a Traditional Natural Red Pigment.

The first total synthesis of carthamin (3), a historic natural red pigment, has been achieved. The molecular structure was efficiently constructed by assembling two equivalents of the in situ generated lithiated monomers and triisopropyl orthoformate. This synthesis confirms the structure proposed in 1996.

Atmospheric CO captured by biogenic polyamines is transferred as a possible substrate to Rubisco for the carboxylation reaction.

Biogenic polyamines are involved in a wide range of plant cellular processes, including cell division, morphogenesis and stress responses. However, the exact roles of biogenic polyamines are not well understood. We recently reported that biogenic polyamines that have multiple amino groups can react with CO and accelerate calcium carbonate formation in seawater.

Biogenic polyamines capture CO2 and accelerate extracellular bacterial CaCO3 formation.

Bacteria, including cyanobacteria, as well as some fungi, are known to deposit calcium carbonate (CaCO(3)) extracellularly in calcium-containing artificial medium. Despite extensive investigation, the mechanisms involved in extracellular formation of CaCO(3) by bacteria have remained unclear. The ability of synthetic amines to remove carbon dioxide (CO(2)) from natural gas led us to examine the role of biogenic polyamines in CaCO(3) deposition by bacteria.

Synthesis of the pluramycins 2: total synthesis and structure assignment of saptomycin B.

A concise, highly convergent total synthesis of saptomycin B, a member of the pluramycin class of antitumor antibiotics, is reported. The target compound was assembled from four building blocks (a tricyclic platform, two sugars, and an alkynal) in 15% yield through 10 synthetic operations. The key steps included the regioselective installation of two amino sugars (L-vancosamine and D-angolosamine) on the tricycle and the efficient construction of the tetracyclic skeleton by an aldol reaction followed by formation of the pyranone.

Unified approach to catechin hetero-oligomers: first total synthesis of trimer EZ-EG-CA isolated from Ziziphus jujuba.

A catechin hetero-trimer isolated from Ziziphus jujuba has been synthesized. Among three constituent monomers, (-)-epiafzelechin and (-)-epigallocatechin were prepared by de novo synthesis. Trimer formation relied on the unified approach to oligomers based on the bromo-capping and the orthogonal activation, reaching the reported structure of the natural product.

Leishmanicidal activities and cytotoxicities of bisnaphthoquinone analogues and naphthol derivatives from Burman Diospyros burmanica.

A methanol extract of the wood of Diospyros burmanica, collected in Burma (Myanmar), was found to exhibit significant activity against Leishmania major. Subsequent chromatographically resolved fractionation led to the isolation of three novel bisnaphthoquinone analogues, burmanin A, B, and C (1-3), together with nine known compounds (4-12). The structure of 1 was confirmed by X-ray crystallography, and those of 2 and 3 by spectroscopic techniques, including 1D and 2D NMR.

Chlorpromazine oligomer is a potentially active substance that inhibits human D-amino acid oxidase, product of a susceptibility gene for schizophrenia.

D-amino acid oxidase (DAO), a potential risk factor for schizophrenia, has been proposed to be involved in the decreased glutamatergic neurotransmission in schizophrenia. Here we show the inhibitory effect of an antipsychotic drug, chlorpromazine, on human DAO, which is consistent with previous reports using porcine DAO, although human DAO was inhibited to a lesser degree (K(i) = 0.7 mM) than porcine DAO.

New sulfoalkylresorcinol from marine-derived fungus, Zygosporium sp. KNC52.

A new sulfoalkylresorcinol (1) was isolated from the marine-derived fungus, Zygosporium sp. KNC52. The structure of 1 was elucidated by spectroscopic methods including MS and NMR, and the absolute stereochemistry was determined by the modified Mosher's method.

Structure revision of circumdatins A and B, benzodiazepine alkaloids produced by marine fungus Aspergillus ostianus, by X-ray crystallography.

The structures of circumdatins A and B, pentacyclic alkaloids produced by Aspergillus ostianus, were revised from the previously reported betaine structures to unique oxepin ones by X-ray crystallography. The co-occurring known alkaloids, circumdatins D, E, and H, and a new compound reported here, circumdatin J, have a common framework.

Brominated unsaturated fatty acids from marine sponge collected in Papua New Guinea.

New brominated fatty acids (3, 5-8, 10) and new sterol esters (14-16) have been isolated from an unidentified marine sponge collected in Papua New Guinea. Their structures were determined on the basis of their spectroscopic data. A major component of the marine sponge (1) was tested for activities against Arutemia salina and some fungi.

Three new polyketide-terpenoid hybrids from Penicillium sp.

Three novel hybrid polyketide-terpenoid metabolites were isolated from a Penicillium minioluteum strain. Their structures were determined by NMR spectroscopic analyses and X-ray crystallography. The proposed biosynthetic pathway including a unique retro-Claisen migration of methyl carbonate correlates the three compounds with berkeleydione and berkeleytrione.

Isolation of new aliphatic sulfates and sulfamate as the Daphnia Kairomones inducing morphological change of a phytoplankton Scenedesmus gutwinskii.

New aliphatic sulfates and sulfamates were isolated from Daphnia pulex as the Daphnia kairomones that induced morphological defense of a freshwater phytoplankton Scenedesmus gutwinskii var. heterospina (NIES-802). Their structures were determined by spectroscopic and synthetic studies.

Isolation and absolute configuration determination of aliphatic sulfates as the Daphnia kairomones inducing morphological defense of a phytoplankton-part 2.

4,8-Dimethylnonyl sulfate (1) and 3-methyl-4E-decenyl sulfate (2) were isolated from Daphnia pulex as the Daphnia kairomones that induced morphological defense of a freshwater phytoplankton Scenedesmus gutwinskii var. heterospina (NIES-802). The absolute configuration at C4 of 1 was determined by Ohrui's method applied to alcohol 3.

Antileishmanial compounds from Cordia fragrantissima collected in Burma (Myanmar).

A methanol extract of the wood of Cordia fragrantissima, collected in Burma (Myanmar), was found to exhibit significant activity against Leishmania major. Bioassay-guided fractionation of this extract using several chromatographic techniques afforded three new compounds (1-3) and five known compounds (4-8). The structures of the new compounds were revealed on the basis of spectroscopic data interpretation and by X-ray crystallographic analysis.

New cytotoxic 14-membered macrolides from marine-derived fungus Aspergillus ostianus.

Three new 14-membered macrolides, named aspergillides A, B, and C (1, 5, and 7), were isolated from marine-derived fungus Aspergillus ostianus strain 01F313, cultured in a medium composed of bromine-modified artificial seawater. The structures of the new compounds were determined by analyses of 1D and 2D NMR spectra. Their absolute configurations were elucidated by the modified Mosher's method and chemical conversions.

Pentaketides relating to aspinonene and dihydroaspyrone from a marine-derived fungus, Aspergillus ostianus.

Three new pentaketides, aspinotriols A ( 1) and B ( 3) and aspinonediol ( 5), were isolated together with two known compounds, aspinonene ( 7) and dihydroaspyrone ( 9), from the marine fungus Aspergillus ostianus strain 01F313, which was collected in Pohnpei and cultured with bromine-modified artificial seawater. The structures of the new compounds were determined by spectroscopic analyses including 1D and 2D NMR. Although 1 and 3 are diastereomers, they show nearly superimposable (1)H and (13)C NMR spectra.

Unusual transannular cyclization products of sarcophytoxide, a 14-membered marine cembranoid: anomalous stereochemistry of epoxide-ketone rearrangement.

[reaction: see text] Treatment of sarcophytoxide with trimethylsilyl trifluoromethanesulfonate afforded an aromatic ketone as an unusual cyclization product. The modified Mosher's method and X-ray analysis performed on the aromatic ketone revealed that it is a 4:1 mixture of 8(R)- and 8(S)-enantiomers. It also suggested that the precursor ketone has 8(R)-configuration, which is contradictory to that expected from the ordinary epoxide-ketone rearrangement.

Isolation and absolute configuration determination of aliphatic sulfates as the Daphnia kairomones inducing morphological defense of a phytoplankton.

2,6-Dimethylheptyl sulfate (1) and 6-methyloctyl sulfate (3) were isolated from Daphnia pulex as the Daphnia kairomones that induced morphological defense of a freshwater phytoplankton Scenedesmus gutwinskii var. heterospina (NIES-802). The absolute stereochemistry at C2 of 1 was determined by (1)H-NMR analysis of the (R)-MTPA ester of alcohol 2.

Anti-Helicobacter pylori compounds from Santalum album.

Six new sesquiterpenes, (Z)-2beta-hydroxy-14-hydro-beta-santalol (1), (Z)-2alpha-hydroxy-albumol (2), 2R-(Z)-campherene-2,13-diol (3), (Z)-campherene-2beta,13-diol (4), (Z)-7-hydroxynuciferol (5), and (Z)-1beta-hydroxy-2-hydrolanceol (6), together with five known compounds, (Z)-alpha-santalol (7), (Z)-beta-santalol (8), (Z)-lanceol (9), alpha-santaldiol (10), and beta-santaldiol (11), were isolated from Santalum album, by using bioassay-guided fractionation for Helicobacter pylori. The structures were determined by extensive NMR studies. The absolute configuration of compound 3 was determined by a modified Mosher method.

Inhibitory action of novel arginine derivative on catecholamine secretion evoked by acetylcholine from cultured bovine adrenal chromaffin cells.

A novel product, 4-amino-5-guanidinopentanoic acid 15-[(4-aminobutyl)-3-aminopropylcarbamoyl] pentadecyl ester (Arg-HSA-Spm), was synthesized based on ptilomycalin A, which is one of the extracts from marine sponge. Arg-HSA-Spm contains arginine in its chemical structure. The pharmacological action of Arg-HSA-Spm on catecholamine secretion from cultured bovine adrenal chromaffin cells was examined.

Resolution of 1- and 2-naphthylmethoxyacetic acids, NMR reagents for absolute configuration determination, by use of L-phenylalaninol.

Racemic 1- and 2-naphthylmethoxyacetic acids (1NMA and 2NMA), the chiral anisotropic reagents used for absolute configuration determination of chiral secondary alcohols and primary amines, were conveniently resolved to enantiomers (>99% ee) by condensation with L-phenylalaninol (2-amino-3-phenylpropanol), chromatographic separation of the diastereomers, and hydrolysis. This method enables large-scale preparation of enantiomeric 1NMA and 2NMA.

Oxidation of cyclopropane terpenoids with ruthenium tetraoxide.

Oxidation products of cyclopropanoid terpenes, (-)-carane (4), (+)-cyclosativene (5), laurinterol methyl ether (6), and thujopsane (7), with ruthenium tetraoxide were investigated.

Mechanism of potent antiperoxidative effect of capsaicin.

The effect of a pungent ingredient of red pepper, capsaicin, on lipid peroxidation of rat liver mitochondria (RLM) induced by ADP/Fe(2+) was studied. Capsaicin inhibited the lipid peroxidation significantly, being more effective than the well-known antioxidant alpha-tocopherol. Capsaicin was also found to scavenge 1,1'-diphenyl-2-picrylhydrazyl (DPPH) radicals both in solution and in membranes, especially the latter.