An approach to the synthesis of bruceantin. The synthesis of a tetracyclic intermediate

Publisher Website
Google Scholar
Abstract
An intermediate (20) containing four of the five rings and seven of the ten chiral centers of bruceantin (1) was prepared. In a key reaction, 3-iodo-1-trimethylsilyl-5-hexen-1-yne (9) was found to add chemoselectively and stereoselectively to a dianion. The sequence also includes a selective attack by a sulfinate (17) on the terminal acetylene C-atom of the dianion of a keto acetylene, a concomitant cyclization in which the acetylene acts as an electrophile, and the use of the resulting allyl sulfoxide for the introduction of oxygen functionality by a reductive rearrangement. Keywords: bruceantin, sigmatropic rearrangement, stereoselective alkylation.