Tandem cyclization and acetalization of a homologated D-glucose delivers D-glycero-D-guloseptanosides

Abstract

A synthesis of methyl-D-glycero-D-gulo-septanoside and allyl D-glycero-D-gulo-septanoside from a D-glucose derived heptenitol is reported. Key steps in the synthesis include the diasteroselective dihydroxylation of the heptenitol, regioselective opening of the benzylidene protected diol and the tandem cyclization-acetalization that delivers the guloseptanosides. The facility in formation of the alkyl septanosides suggests that the cyclic hemi-acetal 2 is favored over the acyclic hydroxy-aldehyde 3 when they are able to equilibrate. The results here set the groundwork for the preparation of more complex septanosides by this route.