44 タキサン型ジテルペンの合成研究 : その3

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This paper reports our synthetic studies on the optically active taxa-4 (20),11-diene deriv. (1), in which segment A-II (23) and segment B (3) are utilized as the building blocks. I. Synthesis of Segment A-II (23) The allyl alcohol (17), which was synthesized from d-camphor (10) through the similar reaction pathway as carried out in the synthesis of segment A-I (2), was converted to the aldehyde (19) via 18. 19 was treated with alkali to convert to 21 whose 1R configuration is same as the C-1R configuration in the taxane-skeleton. 21 was then smoothly converted to segment A-II (23). II. Coupling of Segment A-II (23) and Segment B (3) The coupling was effected by use of t-BuLi in DME-HMPA (3: 1) to furnish 24, which, via 25, was readily converted to the hydroxy-ketone (26). III. Examination for the Construction of Taxane-Skeleton Thioketal-mesylate (28a), -bromide (28b), ketal-mesylate (30a), and -bromide (30b) were prepared from 26 via 27 and their cyclization (formation of the B-ring of taxane-skeleton) was examined under various basic conditions, but without success. Then, after some model experiments (32-37), 29 was converted to the 12-membered lactone (40). Examination utilizing 40 and the other related compounds towards the formation of the 8-membered B-ring of taxane-skeleton has been carried out and the results will be discussed.
天然有機化合物討論会の論文
1981-09-10