Iron-catalyzed cross-coupling between C-bromo mannopyranoside derivatives and a vinyl Grignard reagent: toward the synthesis of the C31-C52 fragment of amphidinol 3

A chemo- and diastereoselective iron-catalyzed cross-coupling between C-bromo mannopyranoside derivatives and 2-methyl-1-propenylmagnesium bromide was developed. This method was used as the key step for the synthesis of the mirror image of the C31-C40 and C43-C52 fragments of amphidinol 3 (AM3). These syntheses were achieved from a common trans-tetrahydropyran derived from d-mannose.