25 dl-ジェフィロトキシン,dl-ジヒドロジェフィロトキシンの全合成

概要

論文の詳細を見る
A total synthesis of dl-gephyrotoxin (1), an alkaloid isolated from skin extracts of the Columbian frog, Dendrobates histrionicus has been achieved. A total synthesis of dl-dihydrogephyrotoxin (2), a structure tentatively assigned to a minor Dendrobatid alkaloid, is also described. Reduction of 10 followed by Mitsunobu reaction gave 13. The first two steps of the syntheses established the stereochemistry at three asymmetric centers (C-5a, C-6, C-9a) of 1 and 2. The C(3a) asymmetric center was established via cyclization of N-acyliminium ion derived from 16 [16→17]. The undesired C(5) functionality was removed using the procedure of Barton [17→18→19→20]. The C(1) sidechain was introduced as follows. Eschenmoser sulfide contraction of 21 gave 22. The bulky silyl group at C(6) sidechain of 32 directed the stereochemical course of the catalytic hydrogenation [32→35]. The cis-enyne moiety was introduced to C(6) using the method of Yamamoto [37→38]. DIBAL reduction of 38 followed by desilylation gave dl-1. A combination of diene synthesis developed by Matteson and DIBAL reduction was applied to the synthesis of dl-2 [37→40→41→2]. An interesting feature of these syntheses is that no protection-deprotection sequences were required.
天然有機化合物討論会の論文
1982-09-10