Efficient chemo-enzymatic syntheses of pharmaceutically useful unnatural 2'-deoxynucleosides.

Our chemo-enzymatic method was successfully applied to the synthesis of 2-chloro-2'-deoxyadenosine (CdA, cladribine) in two ways: 1) direct conversion of chemically synthesized 2-deoxy-alpha-D-ribose 1-phosphate (dRP) to CdA; 2) a two-step route via 9-(2-deoxy-beta-D-ribos-1-yl)-2, 6-dichloropurine (Cl2Pu-dR, 5).