Acetic Acid → Ethyl 9-[(2R,3R,4S,5R)-3,4-dihydroxy-5-(hydroxymethyl)tetrahydro-2-furanyl]-6-[(2,2-diphenylethyl)amino]-9H-purine-2-carboxylate

Participants

Reaction Steps

To a solution of crude ethyl 9-{(2R,3R,4R,5R)-3,4-bis(acetyloxy)-5-[(acetyloxy)methyl]tetrahydro-2-furanyl}-6-[(2,2-diphenylethyl)amino]-9H-purine-2-carboxylate (Preparation 64) (74.9 g, assumed 0.103 moles) in warm absolute ethanol (330 ml) was added sodium ethoxide (1.2 g, 0.018 moles) in portions over 23 hours. The resultant mixture was stirred for a further 3 hours and then glacial acetic acid (1.5 ml) was added. The mixture was concentrated in vacuo to give the crude product as a light brown foam (63.7 g) that was used as such for the next step. The crude product can be purified by flash chromatography on silica gel eluting with a gradient system of 5% v/v isopropanol in dichloromethane changing to 7.5% v/v isopropanol in dichloromethane changing to 10% v/v isopropanol in dichloromethane followed by crystallisation from tertiary-butyl methyl ether to give the title compound as colourless crystals, m.p. 118–120° C.

Provenance & Evidence