A new synthesis of 2-chloro-2'-deoxyadenosine (Cladribine), CdA).

A new efficient route for the synthesis of 2-chloro-2';-deoxyadenosine (Cladribine), CdA) has been developed. The key step of this method was selective deprotection of the acetyl group at the 2' position; the 3', 5' acetyl groups were not affected. This can be accomplished efficiently with hydroxylamine hydrochloride and sodium acetate in pyridine. The 2' hydroxyl group was removed by the Barton-McCombie reaction. Using this strategy, CdA was prepared in five steps and 31.0% yields.