Patent ID: 8232387

Claim:
A process for making cladribine of formula I comprising: a) coupling a compound of formula II wherein each of R 1 , R 2 and R 3 is independently alkyl, alkenyl, alkynyl or aryl, x is 0, 1 or 2, y is 2, 1 or 0, and R 4 is hydrogen or SiR 1 R 2 R 3 , with a protected 2-deoxy-ribofuranose of formula III wherein each of R 6 and R 7 is independently a hydroxyl protecting group, and R 5 is a leaving group in an organic solvent and in the presence of a sulfonic acid based Lewis or Brønsted acid at a temperature of between about 0° C. to about reflux of the organic solvent to obtain a reaction mixture comprising a β-anomer of formula IV wherein x′ is 0, 1 or 2, y′ is 2, 1 or 0; b) selectively precipitating the β-anomer of formula IV from the reaction mixture to obtain a heterogeneous mixture in the presence of acetonitrile; c) isolating the precipitated β-anomer of formula IV from the heterogeneous mixture to obtain isolated and substantially enriched β-anomer of formula IV; and d) converting the isolated and substantially enriched β-anomer of formula IV to cladribine.