Total synthesis of the postulated structure of fulicineroside.

ABSTRACT

A total synthesis of the proposed structures of fulicineroside and its aglycone fulicinerine is reported. The tetrasubstituted dibenzofuran substructure was accessible either through a Pd-mediated ortho-metalation or by an Ir-catalyzed meta-borylation. The synthesis of the ß,ß,α-linked trisaccharide consisting of D-olivose, L-rhodinose, and L-rhamnose was challenged by the unprecedented ß-linked rhodinose. A Pd-catalyzed ß-selective glycosylation of a 4-epi-rhodinose and a subsequent Mitsunobu inversion provided selectively the ß-linked L-rhodinose-L-rhamnose disaccharide. Comparison with the reported data for the natural product and the aglycone suggests a misassignment of the structure of the natural product.