Purine analogues as amplifiers of phleomycin. VIII. Some Thiazolo[4,5-b]pyrazines and related compounds

Abstract

The preparations of a series of thiazolo[4,5-b]pyrazines by ring closure of 3-aminopyrazine-2-thiols with orthoesters, and potassium ethyl xanthate are described. 2-Amino-5-bromopyrazine-3-thiol with potassium ethyl xanthate gave both 6-bromothiazolo[4,5-b]pyrazine-2-thiol and thiazolo[4,5-b]- pyrazine-2,6-dithiol. Various S-alkyl derivatives are reported. As amplifiers of phleomycin, 2-(5,6-dimethylthiazolo[4,5-b]pyrazin-2-yltho)- NN-dimethylethylamine, 2-{6- (2-dimethylamino- ethylthio)thiazolo[4,5-b]pyrazin-2-ylthio)-N,N-dimethylethylamine, and N,N-dimethyl-2-(2-methyl- thiazolo[4,5-b]pyrazin-6-ylthio)ethylamine each showed moderate activity.