As an alternative method for preparing sugar derivatives having a phosphorus atom as the ring heteroatom', attempts to introduce a carbon-phosphorus bond were made by using the addition reaction of phosphorus compounds to glycosiduloses. It is known that reaction of carbonyl compounds with dialkyl phosphonates affords oc-hydroxyphosphonates', and the reaction of glyculoses with dialkyl phosphonate under Abramov conditions has also been reported3. We now report a stereospecific addition reaction of phosphorus compounds to a glycosid-4-ulose. lMethy1 6-deoxy-2,3-0-isopropylidene-a-L-lyxo-hexop~anosid4ulose4 (1, 2 g) was treated with methyl phenylphosphinate (1.5 g), in the presence of triethylamine (1 mL) as the catalyst, for 10 h at 70-80". The yield of crude product was almost quantitative, and the 'H-n.m.r. spectrum of the reaction mixture showed the existence of only one stereoisomer. The product was recrystallized from methanol, to give pure compound 2a in 45% yield, m.p. 179-180", [LY]~~ -82.3" (c 1.0, CHCl,); ~"2 3320%(0H), 1210 (P=O), 751, and 696 cm-l (Ph); 'H-n.m.r. (CDCl,): 6 1.04 & 0 L 0 \ /" 0 CMez \ 1" CMe2 1 2a