NEW HETEROCYCLIC STRUCTURES - THIAZOLO[3,2-A][1,2,5] THIADIAZOLO[3,4-D]PYRIMIDINE AND [1,2,5]THIADIAZOLO[3',4' 4,5] PYRIMIDO[2,1-B][1,3]THIAZINE - BIOLOGICAL ASSAYS/

lo[3,2-a][1,2,5]thiadiazolo[3,4-d]pyrimidin-9-one, iazolo[3,4':4,5]pyr imido[2,1-b][1,3]thiazin-10-one and its 3-methyl derivative were prepa red by reacting ino-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidin-5-one, ,4- dihydro-2H,6H-pyrimido[2,1-b][1,3]thiazin-6-one or its 3-methyl deriva tive with N-thionylaniline. A reaction mechanism is proposed. The comp ounds and the sodium salts of dro-5H-thiazolo[3,2-a]pyrimidin-5-on-6-y l)sulfamic acid, ,6H-pyrimido[2,1-b][1,3]thiazin-6-on-7-yl)sulfamic ac id and its 3-methyl derivative were tested for antimicrobial and antim ycotic activity on a number of strains, namely: E. Coli, Proteus mirab ilis, P. vulgaris, Pseudomonas aeruginosa, Salmonella spp, Staphylococ cus spp, Streptococcus faecalis, Bacillus subtilis, Sarcina lutea, Can dida albicans, and for antiviral activity on Herpes simplex virus type 1 and Vescicular stomatitis virus. None of the compounds showed antiv iral activity or exhibited biological activity against gram-negative, gram-positive bacteria or against mycetes.