The enantiomerically pure synthesis or 9-[2',3'-dideoxy-2-'3'-bis-C-hydrosymethyl-alpha-L-threorunnosyl]adenine and its 4'-thio analog was achieved via coupling or silylated 6-chloropurine with 1-O-acetyfuranose derivative 17 and its 4'-thio analog 24, respectively, prepared from (+)-diethyl L-tartrate. (C) 1997 Elsevier Science Ltd.