Process for the preparation of 2'-deoxyribofuranosyl nucleosides

Claim 1

A process for the preparation of substantially pure β-anomers of 2'-deoxyribofuranosyl nucleosides of the formula: ##STR5## wherein R 1 represents a hydrogen atom, a straight-chain or branched alkyl group of 1 to 6 carbon atoms, a phenyl or benzyl group, a methoxy group, a halogen atom, a nitro group, a nitrile group, or an amino group which is unsubstituted or mono- or disubstituted by alkyl residues of 1 to 6 carbon atoms, or in which the nitrogen atom thereof can be part of a 5- or 6-membered ring, or a perfluoroalkyl group of 1 to 6 carbon atoms; R 2 is a hydrogen atom or a halogen atom; and R 3 and R 4 represents a benzoyl, tolyl, p-chlorobenzoyl, or p-nitrobenzoyl group, which comprises reacting a 1-halogen derivative of a blocked 2-deoxy-D-ribose having the formula: ##STR6## wherein Hal represents a halogen atom, with a silylated pyrimidine derivative having the formula: ##STR7## wherein R 1 , R 2 , R 3 and R 4 have the above-indicated meanings, in an alkyl nitrile solvent having the formula: R.sup.5 --C.tbd.N IV wherein R 5 represents a straight-chain or branched alkyl group of 1 to 4 carbon atoms, and in the presence of a mercury(II) salt at a temperature of about -10° to about +40° C.; precipitating the desired β-anomer as the only insoluble component by allowing the reaction mixture to stand at a temperature of between about -3° C. to 20° C.; and separating the thus-precipitated β-anomer from the reaction mixture.