Synthesis of the ring system of phomactin D using a Suzuki macrocyclization

[GRAPHICS] The ring system of phomactin D was synthesized in racemic form in an effici ent man ner from 2,3-dimethylcyclohexanone. Notable transformations include (1) an alkylation of the enolate of a vinylogous thiolester to install a q uaternary stereocenter, (2) a conjugate addition of cyanide to an alpha,bet a-unsaturated aldehyde, (3) the formation of a Weinreb amide directly from a cyanohydrin, and (4) an intramolecular Pd-mediated Suzuki coupling of a B -alkyl-9-BBN derivative and a vinyl iodide to form the macrocyclic ring.