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.