Preparation of purines

Abstract

A process for the preparation of a compound of formula (A) wherein: X is hydrogen or hydroxy, chloro, Calkoxy or pheny Calkoxy; and Rand Rare hydrogen, or acyl or phosphate derivatives thereof, which process comprises: (i) the preparation of a compound of formula (I) wherein Ris Calkyl, or phenyl Calkyl in which the phenyl group is optionally substituted; Ris hydrogen, hydroxy, chlorine, Calkoxy, phenyl Calkoxy or amino; and Ris halogen, Calkylthio, Calkylsulphonyl, azido, an amino group or a protected amino group, which preparation comprises the reaction of a compound of formula (II) wherein Rand Rare as defined for formula (I) with a compound of formula (V) wherein L is a leaving group and Ris as defined for formula (I), to give a compound of formula (VI), and thereafter converting the intermediate compound of formula (VI) to a compound of formula (I) via decarboxylation, and as necessary or desired, interconverting variables R, Rand Rto further values of R, Rand R; (ii) the conversion of the resulting compound of formula (I) to a compound of formula (A) by converting variable R, when other than amino, to amino, reducing the ester groups CORto CHOH and optionally forming acyl or phosphate derivates thereof, and as necessary or desired converting variable Rin the compound of formula (I) to variable X in the compound of formula (A); characterized in that Ris chloro in formula (I)