Several new synthetic reactions have been established which are useful to the synthesis of certain important natural products : (1) stereoselective formation of trisubstituted (E) -olefins by means of, π-allylic nickel bromide complexes, (2) stereoselective formation of trisubstituted (E) -allylic alcohols via [2, 3] sigmatropic rearrangement of α-isopropenylamine N-oxides, (3) stereoselective formation of trisubstituted (Z) -allylic alcohols via the Wittig reaction of unstabilized ylids with alkoxyacetones, (4) stereoselective synthesis of trisubstituted (Z) -allylic alcohols via nucleophilic ring opening of erythro-α-methyl-α, β-epoxy alcohols followed by cis-elimination of the resulting 1, 2-glycols, (5) stereospecific coupling of (E) -and (Z) -polyprenyl aryl sulfones with trisubstituted (Z) -allylic chlorides in the presence of PTC and aq. sodium hydroxide, and (6) ortho-selective alkylation of phenols by means of [2, 3] sigmatropic rearrangement of phenoxyisopropylsulfonium alkylids. They provide promising tools to manipulate acyclic terpenoids at the head or terminal position stereoselectively by the aid of easily accessible reagents under mild reaction conditions. Thus the stereoselective synthesis of the following three kinds of natural isoprenoids, i.e., isoprenoid quinones such as coenzyme Q₁₀ and vitamin K, natural polyprenols which include betulaprenol, bacterialprenol and (S) -dolichol, and natural d-α-tocopherol (vitamin E) has been achieved by the application of the above methodologies.

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Starting with (+) - and (-) -limonenes as chiral synthons, syntheses of biologically active compounds such as prostaglandins, (+) -brefeldin A and nepetalactones have been studied. The key-step of these conversions is based on the stereoselective cyclization of 3, 4-disubstituted 4-pentenals into cis-3, 4-disubstituted cyclopentanones using the Rh (I) -complex.
Ring cleavage and reconstruction of five and six membered rings under acetalization conditions are also discussed.

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This review deals with isolation, determination of the structure, conformational analysis and structure-activity relationships of teleocidins. Teleocidins exhibit potent tumor-promoting activity as well as many important biological activities connected with cell proliferation and cell differentiation. Teleocidins and diterpene esters containing TPA are classified as TPA-type promoters because they bind eaqually to the phorbol ester receptor and exhibit their biological activities. Structural requirements for tumor promoting activity, which are common in the TPA-type promoter, are also disccussed.

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Molecular level understanding of a relationship between structure, bonding and reactivity of olefin and allyl complexes of group 10 metals is presented. In addition to three types of olefin complexes previously known, namely 3-coordinated M (O), 4-and 5-coordinated M (II) complexes, a complex containing, π-olefin and, π-allyl ligands simultaneously represents a new type of the group 10 metal-olefin compounds possessing some unique stability, structural and reactivity aspects. Dynamic equilibria and electrophilic substitution of novel σ-allyl-metal complexes are presented. Mechanistic knowledge concerning stoichiometric reactions of π-allyl-metal complexes, namely nucleophilic substitution and reductive elimination, is surveyed and its relevance to actual catalysis is also discussed.

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Contrary to the firm and long-standing credence on the involvement of racemization, the “cationic” 1, 2-rearrangement reactions may proceed stereospecifically under suitable reaction conditions to allow the complete 1, 2-chirality transfer. This fact provides a solid basis for the development of a novel and useful synthetic reactions to achieve the highly selective acyclic steoeocontrol. This paper deals with a survey of the new synthetic methodology based on the novel 1, 2-rearrangements under Lewis acidic conditions as well as the newly exploited silicon-directed relative streocontrol, which would find a broad applicability in the highly stereoselective synthesis of a wide variety of useful compounds including chiral pheromones, macrolides, and so on.

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Synthesis of alkenyl sulfides and their application to carbon-carbon bond forming reactions are described. Both (E) and (Z) -alkenyl sulfides were prepared stereoselectively by the following sequence of reactions : 1) the reaction of electrophiles with 1- (phenylthio) vinyllithium reagents prepared by the treatment of 2-methoxy-alkyl sulfides with twice molar amounts of BuLi. 2) photo-isomerization of alkenyl sulfides. 3) the coupling reaction of Grignard reagents with β- (phenylthio) -β, γ-unsaturated alcohols. New methods for carbon-carbon bond formation at both α and β to the phenylthio group of alkenyl sulfide via thionium ion or 2- (phenylthio) alkyltitanium intermediates were developed. Further alkenyl sulfides were found to be useful intermediates for the preparation of γ-oxoesters, furans, 1-cyclobutenyl ketones, and allenes. The related reactions such as the desulfurizative metallation of sulfides and the synthesis and reactions of cyclobutyl sulfides are also described.

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