PROCESS FOR PREPARING PURINE NUCLEOSIDES

摘要

The present invention provides for the preparation &bgr;-adenine nucleosides by coupling an adenine derivative containing an unprotected exocyclic amino group at the C-6 position and a blocked arabinofuranosyl derivative, in the presence of a base and solvent. The present invention also provides for the stereoselective preparation of 2-deoxy-&bgr;-D-adenine nucleosides wherein a blocked 2-deoxy-α-D-arabinofuranosyl halide is coupled with the salt of an adenine derivative. The forgoing aspects of the present invention are utilized in the preparation of a clofarabine composition wherein the ratio of &bgr; to α-anomer is at least 99:1.