Synthesis, characterization, and coupling reactions of six-membered cyclic P-chiral ammonium phosphonite-boranes; reactive H-phosphinate equivalents for the stereoselective synthesis of glycomimetics

Stereoselective syntheses of P-chiral ammonium phosphonite-borane complexes in the gluco- and manno-like series have been developed from P(V) phostone derivatives. The coupling reactions of these phostone donors with alcohols have been investigated with particular emphasis on the influence of protecting groups and conditions on stereoselectivity. The phosphonite-borane complexes may be applied directly in the coupling reactions and the products oxidized in situ to give phostone-mimetics of disaccharides. On the basis of these studies, successful protocols were established for the synthesis of β-gluco and α- and β-manno-configured phostones of primary alcohols. Deprotection of the dimeric compounds leads to novel families of α- or β-(1→6)-linked glycomimetics.