Stereoselective synthesis of the C1-C11 and C12-C34 fragments of mycalolide A.

A convergent synthesis of the C1-C11 and C12-C34 fragments of mycalolide A is described. Synthetic highlights include a highly E-selective cross-metathesis between a vinyl-functionalized bis-oxazole unit and a polypropionate side chain to introduce the C19-C20 double bond and an enzymatic desymmetrization of a meso-diol in addition to five stereoselective allylations/crotylations to control the 11 stereogenic centers present in the natural product.