反应详情

To a stirred mixture of diethyl (S)-[1-(t-butyldiphenylsilyloxymethyl)-2-hydroxyethoxy]methylphosphonate (540 mg, 1.12 mmol), triphenylphosphine (440 mg, 1.68 mmol) and 2-[bis-(t-butoxycarbonyl)amino]-9-hydroxy-6-methoxypurine (prepared as described in EF-A-319228) (428 mg, 1.12 mmol) in dry THF (20 ml), cooled in ice and under a nitrogen atmosphere, was added dropwise diethyl azodicarboxylate (0.27 ml, 1.68 mmol). Within five minutes complete dissolution had occurred and the ice bath was removed. After 1 hour, the solution was evaporated to dryness and the residue obtained chromatographed on silica gel (initial eluant hexane: ethyl acetate 2:1, then hexane:ethyl acetate in the proportions 1:1, 1:2, 1:3) to yield (S)-2-[bis-(t-butoxycarbonyl)amino]-9-[3-(t-butyldiphenylsilyloxy)-2-(diethoxyphosphorylmethoxy)propoxy]-6-methoxypurine as a colourless glass (310 mg, 32%). 1H NMR: δH [(CD3)2SO] 0.96 (9H, s, t-Bu), 1.18, 1.19 (2×3H, 2×t, J= 7 Hz, (OCH2CH3)2), 1.37 (18H, br.s, 2×t-Bu), 3.7-4.15 (12H, m, CHCH2, (OCH2CH3)2, OCH2P, OCH3), 4.45-4.70 (2H, m, NOCH2), 7.25-7.75 (10H, m, 2×Ph), 8.75 (1H, s, H-8). m/z: (FAB+ve ion, thioglycerol/HCl) 844 (MH+, 4%), 644 (100%).

1. temperaturecooled in ice and under a nitrogen atmosphere
2. dissolutionWithin five minutes complete dissolution
3. customthe ice bath was removed
4. customthe solution was evaporated to dryness
5. customthe residue obtained
6. customchromatographed on silica gel (initial eluant hexane: ethyl acetate 2:1