Thiobases in Escherchia coli Transfer RNA: 2-Thiocytosine and 5-Methylaminomethyl-2-thiouracil.

Two new sulfur-containing pyrimidine nucleotides have been isolated from hydrolyzates of Escherichia coli transfer RNA. The structures, 2-thiocytosine and 5-methylaminomethyl-2-thiouracil, have been assigned to the bases as a result of study of ultraviolet and mass spectra. An acid-degradation product, S-methylamino-methyluracil, has been synthesized and is identical to that derived from the natural product.