Syntheses of Papyracillic Acids: Application of the Tandem Chain Extension–Acylation Reaction

A synthetic approach to the papyracillic acid family
of natural
products has been developed. The spiroacetal core is rapidly assembled
through an unprecedented zinc carbenoid-mediated tandem chain extension–acylation
reaction. Subsequent functional group manipulation provided access
to papyracillic acid B and 4-epi-papyracillic acid
C. The successful preparation of these molecules resulted in the clarification
of structural assignments of members of this family of natural products.