Synthesis and hypnotic activities of 4-thio analogues of N-3-substituted uridines

Reaction of tri-O-acetyluridine (1) with benzyl bromide or 2-chloroacetophe none in the presence of K2CO3 gave the N-3-Substituted analogues 2a,c. Cond ensation of 1 with (+/-)-1-phenylethanol or 3,5-dimethylbenzyl alcohol usin g the Mitsunobu reaction also gave 2b, d in good yields. These compounds we re allowed to react with Lawesson's reagent and were subsequently treated w ith ammonia to afford the 4-thiouracil derivatives 5a-d. Compounds 5a-c sho wed moderate hypnotic activity in mice. However, N-3-(3,5-dimethyl)benzyl d erivatives 3d, 5d were found to be almost inactive in this assay.