Abstract: 2'-Deoxyribofuranosyl nucleosides having the formula: ##STR1## , wherein R.sup.1 is a hydrogen atom, a straight-chain or branched alkyl group of 1-6 carbon atoms, a phenyl or benzyl group, a methoxy group, a halogen atom, a nitro group, a nitrile group or an amino group which can be mono- or disubstituted by alkyl of 1-6 carbon atoms, or in which the nitrogen atom thereof is part of a 5- or 6-membered ring, or a perfluoroalkyl group of 1-6 carbon atoms; R.sup.2 is a hydrogen atom or a halogen atom; and R.sup.3 and R.sup.4 are benzoyl, tolyl, p-chlorobenzoyl or p-nitrobenzoyl, which comprises reacting a 1-halogen derivative of a blocked 2-deoxy-D-ribose with a silylated pyrimidine derivative in an alkyl nitrile solvent in the presence of a mercury (II) salt at a temperature of about -10.degree. to about 40.degree. C. The biologically active .beta.-anomers can be separated from the resulting reaction mixture readily and in high yield.