Enantioselective Total Synthesis of (+)-Taxusin

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 Me 2 AlOTf 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.