Approach to the Synthesis of the C1-C11 and C14-C18 portion of Leucascandrolide A.

An asymmetric synthesis of the C1 to C11 and C14 to C18 fragments of the macrocyclic portion of the antibiotic Leucascandrolide A was achieved in 21 total steps from an achiral dienoate. The key 4-hydroxy-2,5-pyran portion of the natural product was established by oxy-Michael cyclization of a 5,7,9,11-tetraol intermediate, which in turn was established by an iterative asymmetric-hydration of dienoates. Alternative strategies for establishing the polyol stereochemistry were explored.