Fluorinated pyrrolo[2,3-d]pyrimidine nucleosides: 7-fluoro-7-deazapurine 2 `-deoxyribofuranosides and 2 `-deoxy-2 `-fluoroarabinofuranosyl derivatives

Abstract

The syntheses of 7-deaza-7-fluoro-2'-deoxyadenosine (1a), 7-deaza-7-fluoro-2'-deoxyinosine (3a) and 7-deaza-7-fluoro-2'-deoxyguanosine (3c) as well as of the 2'-deoxy-2'-fluoroarabino-furanosyl derivatives 1b, 3b are described. Starting materials were 6-chloro-7-fluoro-7-deazapurine (4-chloro-5-fluoropyrrolo[2.3-d]pyrimidine, 4b) and 2-pivaloylamino-6-chloro-7-fluoro-7-deazapurine (2-pivaloylaniino-4-chloro-5-fluoropyrrolo[2.3-d]pyrimidine, 6). Nucleobase anion glycosylation of 4b or 6 with the halogenoses 7 or 9 furnished the protected beta-D-nucleosides 8. 10 and 11, which were converted to compounds 1a, 1b by ammonolysis and to 2a-c by sodium methoxide treatment. The 2'-deoxymosine derivatives 3a, 3b and the guanosine analogue 3c were obtained from 2a-c. Conformational analysis of the nucleosides 1a, 1b was performed in solution and in the solid state. Single-crystal X-ray analyses showed that the sugar moiety of 1a exhibits the S-conformation (P = 164.8 degrees, tau = 40.1 degrees). In solution the 2'-fluoro sub-stituents shift the sugar conformation slightly towards N.