Stereoselective Synthesis of Secondary and Tertiary Boronic Esters via Matteson Homologation.

Matteson homologations of chiral boronic esters with lithium dichlorocarbenoids and various nucleophiles proved to be a useful method for the synthesis of functionalized polyketides in a highly stereoselective fashion. Via repeated homologation steps, only 1,2- anti - and 1,3- syn -configured products were obtained. Homologation with substituted carbenoids followed by reaction with carbon nucleophiles resulted in configurationally inverted products and tertiary boronic esters in a highly stereoselective fashion. This approach significantly expands the potential of the Matteson reaction.