1,4-Pentenyne as a five-carbon synthon for efficient and selective syntheses of natural products containing 2,4-dimethyl-1-penten-1,5-ylidene and related moieties by means of Zr-catalyzed carboalumination of alkynes and alkenes

Abstract

Two highly efficient protocols for enantioselective synthesis of 2,4-dimethyl-1-penten-1,5-ylidene derivatives involve the combined use of the Zr-catalyzed methylalumination of alkynes (ZMA) and the Zr-catalyzed asymmetric carboalumination of alkenes (ZACA). The ZMA/ZACA protocol has been applied to the synthesis of a nafuredin intermediate 14 and a potential intermediate 18 for milbemycin beta 3, while the ZACA/ZMA protocol has been applied to the synthesis of a (-)-bafilomycin A(1) intermediate 25.