I The synthesis of papyracillic acids: Application of the tandem chain extension-acylation reaction II Diastereoselective synthesis of beta-methyl-gamma-keto esters through the utility of an L-serine auxiliary

The development of the zinc-mediated tandem chain extension-acylation reaction for the synthesis of spiro-fused ketals was successfully accomplished. The incorporation of a methyl-substituent into the gamma-keto ester backbone, through a methyl substituted carbenoid, allowed for the synthesis of papyracillic acid B and 4-epi-papyracillic acid C. Comparison between the reported and experimental spectral data for papyracillic acid B and 4- epi-papyracillic acid C permitted structural and stereochemical reassignment. Diastereoselective syntheses of beta-methyl-gamma-keto esters were achieved through the utility of an L-serine auxiliary. Preparation of a series of L-serine derived precursors were prepared and studied