Asymmetric Total Synthesis and Revision of Absolute Stereochemistry for (+)-Taumycin A: An Approach that Exploits Orthogonally Protected Quasienantiomers

The first asymmetric total synthesis of C(9)-S-(+)-taumycin A is now reported using an approach that targeted both C(9) diastereomers concurrently. To facilitate this work, we called upon the symmetrical nature of a C(5)-C(13) side-chain intermediate and exploited orthogonal protecting groups as a tactic to access both stereoisomers from a single chiral, nonracemic intermediate. In addition to our successful approach, several minor detours that helped refine our strategy and a detailed analysis of ¹H NMR data will be discussed. Select compounds included in this work were screened against the NCI60 cell line panel and displayed modest growth inhibition activity.

Reiterative epoxide-based strategies for the synthesis of stereo-n-ads and application to polypropionate synthesis. A Personal Account

The enantioselective synthesis of polypropionates continues to be an attractive realm for the synthetic chemists mostly due to the challenges presented by the number of consecutive stereogenic centers contained within the aliphatic chain. Over the years, our laboratory has developed an epoxide-based three-step reiterative methodology for the construction of these targets, with the ultimate goal that the approach could be extended to the synthesis of polypropionate-containing natural products. The key steps include the diastereoselective epoxidation of allylic and homoallylic alcohols, and the regioselective cleavage of 2-methyl-3,4-epoxy alcohols. The choice of the organometallic reagent, and the cis/trans geometry of the chiral epoxide can be used to control both the relative and absolute configuration of the resulting propionate unit, allowing our approach to be applied in the synthesis of advanced fragments. Additionally, the combination of our first- and second-generation methodologies permits the incorporation of different variations at the methyl moiety.