PROCESS FOR PREPARING PURINE DERIVATIVES

The present invention relates to a process for preparing a compound of formula [I], said process comprising the steps of:(i) forming a reaction mixture comprising (a) a compound of formula [II], (b) a compound of formula [III] and (c) 1 ,2-propanediol or polyethylene glycol, or a mixture thereof, and optionally (d) a base;(ii) heating said reaction mixture to a temperature of at least about 150°C to form a compound of formula [I];(iii) isolating said compound of formula [I]; and(iv) optionally converting said compound of formula [I] into salt form;wherein:R1 and R2 are each independently H, alkyl or haloalkyl;R3 and R4 are each independently H, alkyl, haloalkyl or aryl;R5 is alkyl, alkenyl, cycloalkyl or cycloalkyl-alkyl, each of which may be optionally substituted with one or more OH groups;R6 is selected from cyclopropylamino, cyclopropylmethylamino, cyclobutylamino, cyclobutylmethylamino andwhere one of X, Y and Z is N and the remainder are CR9;R7, R8 and each R9 are independently H, alkyl or haloalkyl, wherein at least one of R7, R8 and R9 is other than H.Further aspects of the invention relate to a highly diastereoselective process for the preparation of compounds of formula [III], a process for preparing intermediates of formula [II], and other intermediates useful in the synthesis of compounds of formula [I], and to a process for preparing the crystalline tartrate salt and free base of compounds of formula [I].