[Synthesis and characteristics of five phosphates of L-glycero-D-manno-heptose]

Five monophosphates of L-glycero-D-manno-heptose having the PO(OH)2 residue at O-2,3, 4, 6, and 7 have been synthesized starting from suitably protected benzyl D-mannopyranoside derivatives. The synthesis involved chain elongation by the reaction of D-mannoside 6-aldehyde with alkoxymethylmagnesium chloride resulting in the desired L-glycero-D-manno-heptopyranoside as the main product. The blocking groups pattern enabled selective deprotection of the hydroxyl groups at C-2, 3, 4, and 7. These substrates were phosphitylated with 2-dimethylamino-5,6-benzo-1,3,2-dioxaphosphepan and oxidized in situ to phosphates. The resulting products were hydrogenolytically deprotected and converted to di(cyclohexylammonium) salts which were characterized by 13C-NMR spectra.