Scheme 12.

3- hydroxypropylsulfanyl derivative used as an intermediate for the synthesis of several other derivatives, such as corresponding acetyl, carbonate, ethyl 8-methyl-6-(3-nitrophenyl)- 3,4-dihydro-2H,6H-pyrimido [2,1-b]thiazine-7-carboxylate derivatives, and their corresponding experimental conditions are provided. However, phenylsulfonate ester derivative was not obtained from the reaction between 3- hydroxypropylsulfanylderivative and benzenesulfonyl chloride in dry pyridine, which was stirred overnight.