Marine microorganisms are of considerable current interest as a new promising source of bioactive substances. Recently marine microorganisms have proven to produce a variety of chemically interesting and biologically significant secondary metabolites and some of them are expected as lead compouds for drug development or pharmacological tools for basic studies on life sciences. Here we describe the review of the recent studies on bioactive substances isolated from marine microorganisms such as bacteria, fungi, blue-green algae, dinoflagellates, and others.

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As part of our ongoing research efforts into the synthesis and biological evaluation of quinone derivatives, we have established synthetic methodologies for preparing unique quinone compounds possessing multiprenyl groups, chemically modified multiprenyl groups, ethylenic and acetylenic bonds, and sterically hindered groups. Biological effects of the quinone derivatives on the enzymes 5-lipoxygenase and thromboxane A₂ synthase, and on thromboxane A₂ receptor and other spasmogenic prostanoid receptors, have been evaluated and discussed. Enzyme inhibitors and receptor antagonists involved in the arachidonic acid cascade system represent a new class of drugs that could potentially treat certain sequelae of asthma, septic shock, thrombosis, stroke, and various other human disorders. It was found that the quinone derivative 2- (12- hydroxy-dodeca-5, 10-diynyl) -3, 5, 6-trimethy1-1, 4-benzoquinone (AA-861) proved to be a potent and specific inhibitor of 5-lipoxygenase and that 7- (3, 5, 6-trimethy1-1, 4-benzoquinon-2-yl) -7-phenylheptanoic acid (AA-2414) was a non-prostanoid thromboxane A₂ receptor antagonist.

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Dimethyl triarylmethylphosphonates, 1, 1, 1-triary1-2-alkynes, and triarylmethylcycloalkanes underwent photochemical α, α-elimination of two aryl groups to give biaryl and the corresponding arylcarbene intermediates, respectively. Moreover, 1, 1, 1-tripheny1-2-alkene or methyl triphenylacetate also underwent another type of α, α-elimination of a phenyl group and an alkenyl group or a methoxycarbonyl group to give phenylakene or methyl benzoate, and diphenylcarbene intermediates, respctively. Triarylacetonitrile and (triphenylmethyl) diethylamine mainly underwent C-CN or C-N bond cleavage to give triarylmethane or triarylmethyl methyl ether in methanol solution. These photochemical α, α-eliminations can be understood in terms of a special example of di-π-methane or oxa-di-π-methane rearrangement through a singlet excited state.

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2-Isoxazolines (4, 5-dihydroisoxazoles) are recognized as useful intermediates in organic synthesis. The synthetic utilites of them are as follows : Firstly, they are readily prepared via an inter- or an intramolecular 1, 3-dipolar cycloaddition of nitrile oxides. Secondly, they can be converted into various important synthetic units such as β-hydroxy ketones or γ-amino alcohols. The isoxazoline strategy can be regarded as an aldol alternative strategy for construction of aliphatic and alicyclic compounds. In this review, recent development of the chemistry of 2-isoxazoline is described. I focus my attention to the following three topics : the stereo- and regiochemical course of the intermolecular 1, 3-dipolar cycloaddition reaction of nitrile oxides, the stereochemical course of intramolecular 1, 3-dipolar cycloaddition of nitrile oxides, and the stereoselective constructionof side chains of 2-isoxazolines.

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In 1989, we succeeded in demonstrating the first example of an asymmetric Heck reaction. Treatment of the prochiral alkenyl iodide 4 b with Cl₂Pd (R) -BINAP (10 mol%), Ag₃PO₄ (2 molar equiv) and CaCO₃ (2.2 molar equiv) in 1-methyl-2-pyrrolidinone produced the cis-decalin derivative 8 b with 80% ee. The result suggested that the presence of a silver salt produced the Pd⁺ intermediate 11 with 16-electron configuration by abstraction of I^- to result in the formation of 8 b with high ee. Under the similar conditions, the cis-decalin derivative 18 of 92% ee and the cis-hydrindan derivative 26 a of 86% ee were obtained from the corresponding alkenyl iodides, respectively, On the other hand, it was found that treatment of the prochiral alkenyl triflate 19 d with Pd (OAc) ₂ (5 mol%), (R) -BINAP (10 mol%) and K₂CO₃ (2 molar equiv) in toluene gave 8 d in 91% ee. Furthermore, 27 was cyclized to 26 b in 73% ee under the similar conditions, which was successfully transformed into the key intermediate 34 for oppositol. An asymmetric Heck reaction was also useful for the synthesis of polycyclopentanoids. Thus, the prochiral alkenyl triflate 59 was treated with 1.7 mol% of Pd (0Ac) ₂, 2.1 mol% of (S) -BINAP and 1.7 equiv of tetrabutylammonium acetate in DMSO afforded the cyclopentanoid 60 of 80% ee in 89% yield. The reaction was found to be useful as well for the capture by a C-centered nucleophile instead of tetrabutylammonium acetate, giving 68 c of 80% ee in one-step from 59. The cyclopentanoid 60 was converted to 43 in a seven-step process, which is a key synthetic intermediate for capnellenols.

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