Enantioselective total synthesis of taxol has been accomplished. Coupling reaction of the optically pure A-ring hydroxy aldehyde with the aromatic C-ring fragment followed by Lewis acid mediated eightmembered B-ring cyclization gave the desired ABC endo-tricarbocycle. The C-ring moiety of this product was reduced under Birch conditions to the cyclohexadiene derivative, which was oxygenated by singlet oxygen from the convex β-face to give the C4β,C7β-diol stereoselectively. For introduction of the C19-methyl, the cyclopropyl ketone was prepared via cyclopropanation of the C-ring allylic alcohol or conjugate addition of a cyano group to the C-ring enone. Reductive cleavage of the cyclopropane ring followed by isomerization of the resulting enol to the corresponding ketone gave the crucial synthetic intermediate containing the C19methyl group. Regioselective transformation of three hydroxyl groups of this intermediate, conversion of the C4-carbonyl group to the allyl chloride, and introduction of the C10-oxygen functionality afforded a precursor for D-ring construction. Dihydroxylation of the allyl chloride moiety followed by basic treatment of the resulting diol gave a fully functionalized taxol skeleton. Functional group manipulation of this product including attachment of the C13 side chain provided (-)-taxol.

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[reaction: see text] Only 1-3 mol % of PtCl(2) or AuBr(3) was sufficient to promote generation and [3+2] cycloaddition of transition-metal-containing azomethine ylides derived from N-(o-alkynylphenyl)imines bearing an internal alkyne moiety. A highly efficient method for the preparation of synthetically useful tricyclic indole derivatives having a substituent at the 3-position of the indole nucleus was established by this method.

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Intermolecular carbon-carbon bond formation between acylsilanes and organoboronic esters was achieved by photoirradiation under almost neutral, transition metal-free conditions. In this reaction, siloxycarbenes generated by photoisomerization of acylsilanes reacted with boronic esters to give the formal B-C bond insertion intermediates, which underwent unique rearrangement to afford the cyclic R-alkoxyboronic esters. Acidic treatment of the resulting crude products under air furnished the crosscoupled ketones in good yields.

Pt(II)-catalyzed generation of unsaturated carbene complex intermediates from various propargyl ether derivatives based on electrophilic activation of alkynes was realized. These in situ generated unsaturated carbene complexes undergo [3+2] cycloaddition reaction with various vinyl ethers, leading to efficient formation of indoles, naphthols, and benzofuran fused with a five-membered ring in high yields.

For the total synthesis of (+)-taxusin, the AC-ring fragment 8 was prepared from an optically active 2-bromo-3-siloxycyclohexenecarbacetal 5 via 4 steps and was converted to the dienol silyl ether 13. The thus-obtained 13 underwent B-ring cyclization in the presence of Me2AlOTf to produce the ABC endo-tricarbocycle 14 having C9α, C10β-substituents, which was converted to the cyclopropyl ketone 21a. Introduction of C19 methyl via reductive cleavage of the cyclopropane ring under Birch conditions and successive in situ treatment of the resulting enol with methanol gave the C3α-protonated ketone 24. Next, 24 was converted to the allylsilane 29, which was then oxidized with m-CPBA to produce the fully functionalized taxusin carbon skeleton. Finally, removal of the silyl protecting groups followed by acetylation completed the total synthesis of (+)-taxusin.

(+)-Grandisol, an insect pheromone having cyclobutane skeleton, is synthesized enantio- and diastereo-selectively. The key steps in the synthesis are the asymmetric [2+2] cycloaddition reaction catalyzed by a chiral titanium reagent and the diastereoselective conjugate addition reaction by the combined use of Me2CuLi and trimethylsilyl trifluoromethanesulfonate.