In the course of synthetic studies on the taxane-type diterpenes, we have been working on the synthesis of optically active taxa-4(16),11-diene deriv.(2). In this paper, our effort for construction of the target structure via combination of segments A (22) and B [(-)-30] is presented. I. Structure Elucidation of 1,1,3-Trimethylcyclohexane Deriv. (5) The structure of 5, the staring material for segment A (22), which was prepared from 1,2,2-trimethylcyclopentane deriv. (4) by use of TBCO via the ring-enlargement reaction, has been elucidated by converting to the ketone (10) via 7, 8, and 9. II. Synthesis of Segment A (22) The allyl alcohol (14), prepared from 5 via 11, 12, and 13, was converted to sec. alcohol (15) by acetylation and SeO_2 oxidation. 15 was then converted via 16 and 17 to 18, which, under basic conditions, was converted to two diastereomers (19, 20). 20, having the C-6 configuration same as the natural taxanes, was converted smoothly to opt. active allyl chloride (22). III. Synthesis of Segment B [(-)-30] Optical resolution of the cyclopropane deriv. (24) was accomplished via HPLC separation of the (+)-(2S,3S)-2,3-butanediol deriv. (25) to furnish (-)-26 and (+)-26. (-)-26 was then converted to the opt. active sulfone [(-)-30] via 27, 28, and 29. IV. Synthesis of Taxa-4(16),11-diene Deriv. (2) Coupling of 22 with (-)-30 was effected by use of t-BuLi to give 31. 31 was then converted to 36 via 32, 33, and bissulfides (34, 35). Derivation of 36 and its deriv. leading to 2 is under study and the results will be discussed.
