Reaction Steps
In accordance with Flowchart D, 2,5-anhydro-D-mannose 26 is treated with acetyl chloride in methanol at reflux, then neutralized with lead carbonate, giving 2,5-anhydro-D-mannose, dimethyl acetal 27. which is treated with sodium hydride and benzyl bromide in dimethylformamide, giving 2,5-anhydro-3,4,6-tris-O-(phenylmethyl)-D-mannose, dimethyl acetal 28. Compound 28 is then treated with tetrafluoroboric acid in acetonitrile, giving 2,5-anhydro-3,4,6-tris-O-(phenylmethyl)-D-mannose 29 which is then treated with Tebbe's reagent in ether at -40° C., then neutralized with sodium hydroxide, giving 3,6-anhydro-1,2-dideoxy-4,5,7-tris-O-(phenylmethyl)-D-manno-hept-1-enitol 30. Compound 30 is treated with osmium tetroxide in pyridine, giving 2,5-anhydro-1,3,4-tris-O-(phenylmethyl)-D-glycero-D-manno-heptitol 31, which is treated with sodium hydride in dimethylformamide, followed by treatment with benzyl bromide, giving 2,5-anhydro-1,3,4,6,7-pentakis-O-(phenylmethyl)-D-glycero-D-manno-heptitol 32. Compound 32 is treated with borontrifluoride etherate in acetic anhydride, giving 2,5-anhydro-3,4,6-tris-O-(phenylmethyl)D-glycero-D-manno-heptitol, 1,7-diacetate 33, which is treated with sodium ethoxide in ethanol, giving 2,5-anhydro-3,4,6-tris-O-(phenylmethyl)-D-glycero-D-manno-heptitol 34. Compound 34 is treated with diethyl phosphorochloridate in pyridine at reduced temperature, giving 2,5-anhydro-3,4,6-tris-O-(phenylmethyl)-D-glycero-D-manno-heptitol, 1,7-bis(diethyl phosphate) 35. Substituting other esterifying agents as described in Flowchart A will result in the corresponding tetraesters. Compound 35 is treated with bromotrimethyl silane in chloroform at reduced temperature, under an inert atmosphere, giving 2,5-anhydro-3,4,6-tris-O-(phenylmethyl)-D-glycero-D-manno-heptitol, 1,7-bis(dihydrogen phosphate) 36, which is then hydrogenated over palladium on carbon in methanol, giving the product of Formula I, where R', R", R'" and R"" are hydrogen,
