Stereocontrolled synthesis of (-)-macrolactin A

A novel, highly convergent, and stereocontrolled synthesis of (;A cuprate derived from(1Z,3E)-5- (1,1-dimethylethyl)dimethylsilyl) oxy-1,3-pentadienyl butyl telluride was used to open the epoxide terminus of the 1,3-diol synthon, ;As a secondary project, synthetic approaches for the preparation of eight-membered carbocycles were evaluated. The Taxol bicyclo(5.3.1) undecene skeleton was the target of a three-prong study which involved the intramolecular cyclization of pendant side chains containing a variety of functional groups onto a conjugated or non-conjugated cyclohexene A-ring. The intramolecular Stille cross-coupling reaction of an acyl chloride tether to a vinyl tri-n-butyl stannane moiety at the C11 (Taxol numbering) position of the A-ring was impeded by protodestannylation. Intermolecular couplings at this position were achieved; however, yields were low due to the sterically congested environment. The cyclization of pendant acyl radicals generated from acyl selenides and tri-n-butyltin hydride in refluxing benzene led to decarbonylation. Upon irradiation with light at room temperature the aldehyde reduction product was favored over cyclization. Finally, the intramolecular cyclopropanation of...