Purine analogues as amplifiers of phleomycin. VII. Some 1H-imidazo-[4,5-b]pyrazines and related compounds

Abstract

Preparations of 2-hydroxy- and 2-mercapto-1H-imidazo[4,5-blpyrazines from pyrazine-2,3-diamines are described. Methylation of 1H-imidazo[4,5-b]pyrazine-2(3H)-thione with methyl iodide and diazomethane gave some S, N1, N3 and N4 methyl derivatives; and 1H-imidazo[4,5-b]pyrazin- 2(3H)-one with diazomethane gave products which involved O, N1, N3 and N4 methylation. These products showed slight activity as amplifiers of phleomycin but the benzothiazoles (10b) and (10c) (as hydrobromides) showed three and four star activity respectively.