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The O-acetylated and O-methylcarbonylated analogue of the methanesulfonate (I) suffer from low product yield or no product formation at all.

A highly diastereo- and enantioselective Diels—Alder reaction of the new precursor α-amino-o-quinodimethane with α,β-unsaturated aldehydes is achieved in the presence of L-proline.

The complete structure of paxisterol 1, produced by a Penicillium species, was determined by means of spectral and chemical studies of the parent compound and several of its derivatives. Paxisterol is a unique sterol, having an acetal structure at C-18. Application of 2D-INADEQUATE technique in 13C NMR spectral analysis was useful in this structure determination, where all carbon-carbon bonds in the molecule were demonstrated. Absolute stereochemistry was confirmed by the CD spectrum of 3-keto derivative 10 of compound 1 to be the same as that of cholesterol. An interesting acetal migration reaction was observed during the chemical conversions.

Seven novel potent antitumor antibiotics, duocarmycins A (1), C1 (2), C2 (3), D (4), B1 (5), B2 (6) and SA (7), were isolated from three independently collected Streptomyces sp. The complete structures, including absolute stereochemistry, were determined by spectral and chemical studies of those duocarmycins and several derivatives. Duocarmycins A (1) and SA (7) possess a 1,2,7,7a-tetrahydrocycloprop[1,2-c]indol-4-one subunit, a common pharmacophore with that of CC-1065 (10) found from Streptomyces zelensis.

o -Tributylstannylmethyl benzaldehyde reacts with Zn in the presence of TMSCl and 2,6 lutidine at room temperature to give α-trimethylsiloxy- o -quinodimethane, which is trapped with dienophiles to afford cycloadducts in good to high yields.

In the course of our screening for new anticancer compounds produced by marine bacteria, we found that a new genus marine bacterium Pelagiobacter variabilis produced new phenazine antibiotics, pelagiomicins A, B and C. Those compounds were labile in water and alcohols. The absolute structure of the main component, pelagiomicin A, and the structures of the minor ones were determined from the spectroscopic data and by synthesis. Pelagiomicin A exhibits activity against Gram-positive and -negative bacteria and antitumor activity in vitro and in vivo.

A novel glycosidic compound, suomilide ( 1 ), was isolated together with 1-( O - α -glucopyranosyl)-3,25-hexacosanediol, a “heterocyst glycolipid” from the non-toxic Nodularia spumigena HKVV. Their structures were determinated by 2D-NMR techniques and MS/MS experiments.

A new xanthine oxidase inhibitor named hydroxyakalone was isolated from the culture broth of a marine bacterium Agrobacterium aurantiacum N-81106. Structure of hydroxyakalone was determined to be 4-amino-1H-pyrazolo[3, 4-d]pyrimidine-3-one-6-ol by the spectral studies of hydroxyakalone and its permethyl derivative. The concentration to induce 50% inhibition (IC50) was 4.6μM against xanthine oxidase.

A novel antibiotic named korormicin was isolated from the marine bacterium, Pseudoalteromonas sp. F-420. This strain was isolated from the surface of a macro alga Halimeda sp. collected from Palau (the Republic of Belau). The planar structure of korormicin was determined by the result of 2D NMR studies and mass spectral data. Korormicin had specific inhibitory activity against marine Gram-negative bacteria, but was inactive against terrestrial microorganisms.

Irradiation of o-formylbenzyltrialkylstannanes in benzene gives α-trialkylstannoxy-o-quinodimethanes which are trapped with dienophiles at room temperature to afford cycloadducts with high stereoselectivities, while the corresponding silane and germane gave a different type of o-quinodimethane and moderate stereoselectivities in cycloadditions.

Seven new macrolactins (named G~M) and known macrolactins A and F were isolated from a culture broth of Bacillus sp. PP19-H3. The strain had been isolated from the macroalga, Schizymenia dubyi. Macrolactin A, which was 24-membered lactone, had previously been reported to show antibacterial, cytotoxic and antiviral activities. The new macrolactins include 22-membered ring or dicyclic lactone in addition to geometric isomers of known macrolactins A and F. The antibacterial activities of all the macrolactins examined in this study were relatively weak.

Details of the recently elucidated biosynthetic pathways of caffeine and related purine alkaloids are reviewed. The main caffeine biosynthetic pathway is a sequence consisting of xanthosine-->7-methylxanthosine-->7-methylxanthine-->theobromine-->caffeine. Genes encoding N-methyltransferases involved in three of these four reactions have been isolated and the molecular structure of N-methyltransferases investigated. Pathways for the catabolism of caffeine have also been studied, although there are currently no reports of enzymatic and genetic studies having been successfully carried out. Metabolism of purine alkaloids in species including Camellia, Coffea, Theobroma and Ilex plants is summarised, and evidence for the involvement of caffeine in chemical defense and allelopathy is discussed. Finally, information is presented on metabolic engineering that has produced coffee seedlings with reduced caffeine content, and transgenic caffeine-producing tobacco plants with enhanced disease resistance.

Hexaarylcyclotrisiloxane, which is one of the most stable derivatives of diarylsilanediol, was found to undergo palladium-catalyzed cross-coupling reaction with aryl halides in good yields. The reaction is performed in an aqueous medium taking potassium hydroxide as an activator. Both of the two aryl groups attached to each silicon atom could be utilized. Some base-sensitive functionality such as acetyl and nitro groups survived the reaction.

Copper (I) and silver carbonyl catalysts were prepared in strong acids such as sulfuric acid, hydrogen fluoride, boron trifluoride-hydrate and fluoro sulfuric acid. Carbonylation of olefins, alcohols, dienes, diols, aldehydes and saturated hydrocarbons were carried out under atmospheric pressure and at room temperature by using copper (I) carbonyl catalyst, and tert-carboxylic acids were prepared in high yield.The highly hindered carboxylic acid was prepared from isobutylene oligomer. The industrial process of highly hindered carboxylic acid was established by using sulfuric acid-phosphoric acid-water mixed solvent in the recycle use of catalyst, and pilot plant started in 1988. This carbonylation method is available to the production of another compound also.The derivatives of highly hindered carboxylic acid is stable to hydrolysis and heat. The usages of this hindered carboxylic acid are paint, microgel, surfactant, stabilizer, initiator of polymerization, agricultural chemicals.

Palladium-catalyzed reactions of heteroaromatic tins with 2-ethoxyallyl diethyl phosphate and of nitrophenyltins with 2-methoxymethoxyallyl chloride were found to give the coupling products, which can be hydrolyzed to the corresponding acetonylated aromatics in good yields.

A variety of gold catalysts can be used to catalyze the oxidation of carbon monoxide at temperatures as low as −70 °C and are stable in a moistened gas atmosphere. The novel catalysts, prepared by coprecipitation, are composed of ultra-fine gold particles and one of the oxides of 3d transition metals of group VIII, namely, Fe, Co, and Ni.

Palladium catalyzed reaction of acyltins with organic halides were investigated. Among the halides, acyl halides and allylic halides were good substrates, and the latter gave allylic ketones in good yields.

Acetates which were derived from primary, secondary, and tertiary alcohols were deoxygenated to the corresponding hydrocarbons in high yield by p-bis(diphenylhydrosilyl)benzene under homolytic conditions.

On fait reagir ici le triphenylsilane dans des conditions radicalaires sur divers furanoses et pyranoses

In the presence of Pd(0) complexes, 2-ethoxy-2-propenyl diethyl phosphate was found to react with organotins to give the corresponding coupling products, showing to be a more efficient halo acetone equivalent compared with the corresponding acetate or carbonate. Reaction with tin enolates gave the 1,4-diketone in moderate to good yields.

2-(Tributylstannyl)-4,4-dimethyl-2-oxazoline (1) reacted with aroyl chloride smoothly without any palladium catalyst to give the unusual product, bis(N-aroyl-4,4-dimethyl-2-oxazolinylidene) in good yields. The reaction of 1 with other types of halide needed a palladium catalyst, and gave the corresponding 2-substituted-4,4-dimethyl-2-oxazoline in good yields.

(α-Ethoxyvinyl)tributyltin acts as a masked acetylating agent in the palladium catalyzed reaction with various organic halides, such as aryl bromides, vinyl bromides, benzyl chloride, and allyl chloride, giving, after hydrolysis of the resulting reaction mixture, good yields of the corresponding ketone product.

Palladium catalyzed reactions of ternary systems involving bromobenzene, t-butyl isocyanide, and organotin compounds were found to occur giving the corresponding imines, although the catalytic efficiencies were rather low.

2,3-Disubstituted norbornenes were prepared by the palladium catalyzed reaction of a ternary system composed of organic halide, organotin compound, and norbornene. Aryl and vinyl bromides, and acyl chloride were good substrates, but benzyl and allyl chlorides were not. Vinyl, phenyl, ethynyl, and allyltin compounds were utilizable reagents.