  A diastereoselective cycloaddition between tetrabromocyclopropene and an annulated furan provided a highly functionalized building block which could be stereo- and chemoselectively manipulated to construct (+)-frondosin A and both enantiomers of frondosin B. Our synthesis of (+) frondosin A represents the second asymmetric total synthesis; consisting of 20 linear steps and a 7.4% overall yield. The two syntheses are highlighted by a Suzuki cross-coupling to introduce requisite aryl functionality along with an unprecedented phosphine mediated ether bridge cleavage. Furthermore, our planned diastereoselective synthesis of frondosin B led to the opposite enantiomeric natural product, suggesting a late stage stereoinversion. Completion of the total synthesis of the natural enantiomer of frondosin A from the identical starting chiral alcohol validated our observation.

Cyclopropene cycloadditions with annulated furans: Total synthesis of (+) frondosin A and (+) and (�) frondosin B

247th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.