A mixture of diisopropyl E-3(1-trityl-1,2,4-triazol-3-yl)prop-2-ene phosphonate (10.31 g, prepared as described in Example 15), N-methyl-morpholine N-oxide (4.69 g) and osmium tetroxide (2.5 ml, 2.5% in t-butanol) in t-butanol-tetrahydrofuran-water (10:3:1, 350 ml) was stirred at room temperature, under nitrogen, for eight hours. Sodium dithionite (10 g) and water (75 ml) were added, the mixture stirred for thirty minutes, filtered and evaporated under reduced pressure. The residue was made weakly acidic with 2M hydrochloric acid, then partitioned between ethyl acetate and brine. The aqueous layer was reextracted with ethyl acetate and the combined organic layers washed with brine, dried over magnesium sulphate and evaporated under reduced pressure. Chromatography on silica, using dichloromethane-ethanol (12:1) as eluant, gave diisopropyl (2RS,3SR)-2,3-dihydroxy-3(1-trityl-1,2,4-triazol-3-yl)propane phosphonate (8.46 g, m.p. 148°-151° C.), 99% pure by GC. NMR (CDCl3): δ1.3(12H,m), 1.88-2.15(2H,m), 3.7(1 H,d), 4.13(1H,d), 4.33(1H,m), 4.6-4.8(3H,m), 7.1-7.4(15H,m), 7.95(1H,s). EI M/S: M+ 549. CI M/S: MH+ 550.
