Synthesis and Antileukemic Activity of Chymotrypsin-Activated Derivatives of 3'-Amino-2', 3'-dideoxycytidine. (Synthetic Nucleosides and Nucleotides, XXXIII)

3'-Amino-2', 3'-dideoxycytidine (8) was directly synthesized from 2'-deoxycytidine. 2', 3'-Dideoxy-3'-(N-acyl-L-phenylalanylamino)cytidines (acyl=butoxycarbonyl (9a), acetyl (9b), benzoyl (9c), and n-hexanoyl (9d)) were synthesized as chymotrypsin-activated prodrugs of 8. This N-protection was required for activation by chymotrypsin to 8. In vitro, compound 8 showed high cytotoxic activity against P388 cells, but the prodrugs 9a-d were ineffective. In vivo, however, these prodrugs showed much higher activity than 8 in mice bearing P388 cells.