Isothiazolopyrimidines--new group of anticancer agents. I.

Synthesis and biological properties of 27 derivatives of 5-amino-3-methylisothiazolo[5,4-d]pyrimidine-4-dione and of 3-methyl-5-semicarbazido-4-isothiazolocarboxylic acid ethyl esters are discussed. 5-Amino-3-methylisothiazolo[5,4-d]pyrimidine-4-dione was converted by reaction with aldehydes into Schiff bases, which under reduction of NaBH4, were transformed into appropriate N-methylene analogs. 3-Methyl-5-semicarbazido-4-isothiazolocarboxylic acid ethyl esters in reaction with aldehydes were converted into benzylidene derivatives. Some of the compounds obtained, especially those of Schiff base structure, displayed strong activity against L-1210 leukemia, Sa-180 sarcoma. Ehrlich carcinoma and Nemeth Kellner lymphoma.