Synthesis of C2-β-Fluoro-Substituted Adenine Nucleosides Via Pivaloyl Derivatives of Adenosine and 3 -Deoxyadenosine

Syntheses of 9-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)adenine (9) its 3-deoxy derivative, 9-(2,3- dideoxy-2-fluoro-β-D-threo-pentofuranosyl)adenine (16), with the DAST treatment of the corresponding 3,5- di-O-pivaloyladenosine (7) and its 3-deoxy derivative 14 are described. The role of the pentofuranose ring stereochemistry of nucleosides 7 and 14 in the DAST fluorination is discussed. Stereochemistry of compounds 7 and 14 as well as fluorides 9 and 16 was studied by the PSEUROT 6.3 program. Keywords: Nucleosides, purine, 2'-deoxyfluoro derivatives, PSEUROT analysis