Synthesis and In Vitro Anticancer Activity of 8-Chloro-3-Cyano-4-Imino-2-Methylthio-4H-Pyrimido [2, 1-B] [1, 3] Benzothiazole and its 2-Substituted Derivatives

8-Chloro-3-cyano-4-imino-2-methylthio-4H-pyrimido [2, 1-b] [1, 3] benzothiazole and its 2-substituted derivatives has been prepared and evaluated at National Cancer Institute, Maryland, USA for their in vitro anticancer activity towards 60 Human Cancer cell lines, derived from various cancer types. Results revealed that all these compounds displayed remarkable anticancer action across human cancer cell lines. Compounds 3, 4c and 4e are selected by NCI for further anticancer activity at five dose concentration level.