Total Synthesis and Stereochemical Reassignment of Citrafungin A.

The stereoselective 12-step total synthesis of the reassigned structure for citrafungin A (1a) via cyclobutene diester 10 is described. Key steps involved a formal [2 + 2]-cycloaddition, oxa-Michael/cyclobutanone ring-opening cascade to secure the alkyl citrate core, and asymmetric vinylzinc addition to form the C6 stereocenter. In addition, no oxidative adjustments are required to secure the citrate oxidation level.