195727-26-5

In spite of exclusive lithiation at the 8-position of 9-(2,3,5-tris-O-TBDMS-β-D-ribofuranosyl)-6-chloropurine (2) with LDA, subsequent quenching of its lithiated species with Bu3SnCl (or TMSCl) results in the formation of 2-substituted products.Under optimized reaction conditions, where LTMP was used as a lithiating agent, 9-(2,3,5-tris-O-TBDMS-β-D-ribofuranosyl)-6-chloro-2-(tributylstannyl)purine (11) was formed in quantitative yield.Several experiments carried out to verify the reaction mechanism suggested that an anionic stannyl (or silyl) transfer from the 8- to the 2-position had been involved.Manipulation of the 2-tributylstannyl group in 11 and its adenine counterpart (22) has disclosed a new entry to 2-substituted purine nucleosides.This chemistry was briefly applied to the synthesis of the 2-fluoro analogue of neplanocin A.

Cladribine, 2-chloro-2'-deoxyadenosine, is a highly efficacious, clinically used nucleoside for the treatment of hairy cell leukemia. It is also being evaluated against other lymphoid malignancies and has been a molecule of interest for well over half a century. In continuation of our interest in the amide bond-activation in purine nucleosides via the use of (benzotriazol-1yl-oxy)tris(dimethylamino)phosphonium hexafluorophosphate, we have evaluated the use of O6-(benzotriazol-1-yl)-2'-deoxyguanosine as a potential precursor to cladribine and its analogues. These compounds, after appropriate deprotection, were assessed for their biological activities, and the data are presented herein. Against hairy cell leukemia (HCL), T-cell lymphoma (TCL) and chronic lymphocytic leukemia (CLL), cladribine was the most active against all. The bromo analogue of cladribine showed comparable activity to the ribose analogue of cladribine against HCL, but was more active against TCL and CLL. The bromo ribose analogue of cladribine showed activity, but was the least active among the C6-NH2-containing compounds. Substitution with alkyl groups at the exocyclic amino group appears detrimental to activity, and only the C6 piperidinyl cladribine analogue demonstrated any activity. Against adenocarcinoma MDA-MB-231 cells, cladribine and its ribose analogue were most active.

A practical process that solves many of the problems of prior art methods for the synthesis of 2-[2-(4-chlorophenyl)ethoxy]adenosine and its analogs is herein presented. This method provides advantages in cost, efficiency, and purity of the final product.