Synthesis and structural elucidation of 2 '-deoxy-4 '-thio-L-threo-pentofuranosylpyrimidine and -purine nucleosides

Benzyl 3,5-di-O-benzyl-2-deoxy-1,4-dithio-L-threo-pentofuranoside (13) was used as glycosyl donor for the synthesis of 4'-thio-L-threo-pentofuranosylu racil derivatives 23-29. The corresponding cytidine analogue 33 was prepare d from 13 via the triazolo derivative 31. Adenine and hypoxanthine did not react with 13. Therefore, 13 was transformed into the 1-O-acetate 15, which was a sufficiently reactive donor for the purine bases, yielding 4'-thio-L -threo-pentofuranosylpurines 36 and 37. In most cases it was possible to ob tain pure anomers of the deprotected nucleoside analogues, three of which w ere suitable for X-ray structural analyses.