Total Syntheses of (+)- and (-)-Tetrapetalones A and C

摘要

Described herein are syntheses of the naturally occurring polyketides (-)-tetrapetalones A and C and their respective enantiomers. The employed strategy involves initial assembly of a masked N-aryl tetramic acid which is advanced via a highly selective conjugate addition/intramolecular Friedel-Crafts acylation sequence to deliver a key azepine intermediate. Application of recently developed C-H activation chemistry and subsequent Heck cyclization delivers the aglycone framework in an overall 12 steps. Resolution of the aglycone via stereospecific glycosylation with an enantiopure glycosyl donor followed by separation of the derived diastereomers enables further advancement to either (+)- or (-)-tetrapetalones A and C.