Synthesis and biological activity of nucleoside antibiotics, ascamycin and its amino acid analogs.

Synthesis of an alanylsulfamoyl nucleoside antibiotic, ascamycin was achieved by the condensation of N6-t-butyloxycarbonyl-2-chloro-9-(2',3'-O-isopropylidene-5'-O-sulfamoyl- beta-D- ribofuranosyl)adenine(3) with t-butyloxycarbonyl-L-alanylimidazole in the presence of NaH in DMF. Deprotection with 90% trifluoroacetic acid gave ascamycin in 61% overall yield. This procedure may be applicable for preparation of a number of amino acid analogs of ascamycin.