Patent ID: 6051709
Filing Date: 2000-04-18
Classification: C07D

Abstract:
In a stereoselective process for producing cis nucleosides of formula (I) ##STR15## wherein W is S, S.dbd.O, SO.sub.2, or O;X is S, S.dbd.O, SO.sub.2, or O;R.sub.1 is hydrogen or acyl; andR.sub.2 is a pyrimidine base or an analogue or a derivative thereof, which comprises the step of reacting the pyrimidine base or an analogue or derivative thereof with an intermediate compound in the presence of a Lewis acid catalyst; said intermediate compound being selected from the group consisting of formulae (IIa) and (IIb): ##STR16## wherein W and X are as defined in formula (I), R.sub.3 is a substituted carbonyl or carbonyl derivative, and L represents a leaving group;wherein the improvement comprises limiting said leaving group to halo, cyano or R.sup.9 SO.sub.2 - wherein R.sup.9 represents alkyl optionally substituted by one or more halo, or optionally substituted phenyl; and said step of reacting the pyrimidine base or analogue or derivative thereof with said intermediate compound is effected without the Lewis acid catalyst.