Synthesis of 4,5-dideoxy-4-C-[(R,S)-phenylphosphinyl]-d-ribo- and l-lyxo-furanose and their 1,2,3-triacetates

2,3- O -Isopropylidene- d -ribose diethyl dithioacetal, prepared from d -ribose, was converted in three steps into the corresponding dimethyl acetal, which was monotosylated at O-5, and the ester oxidized at C-4 with pyridinium chlorochromate; addition of methyl phenylphosphinate to the resulting pentos-4-ulose derivative then provided (4 R,S )-4,5-anhydro-2,3- O -isopropylidene-4- C -[( R,S )-(methoxy)phenylphosphinyl]- d - erythro -pentose dimethyl acetal. Hydrogenation of this compound in the presence of Raney Ni, followed by reduction with SDMA, hydrolysis, and acetylation, yielded the title compounds (seven kinds), the structures of which were established on the basis of their 400-MHz, 1 H-n.m.r. and mass spectra. A general dependence of the 2 J PH and 3 J PH values on the OPCH and PCCH dihedral angles provided an effective method for the assignment of the configurations and conformations of these 4-deoxy-4-phosphinyl-pentofuranoses.