Thiazolopyrimidine derivatives have attracted a great deal of interest owing to their antimicrobial [1], antiviral [2] and antitumor [3] activities. In continuation of our previous study on the application of thiazolopyrimidine moiety in new heterocyclic ring syntheses, we demonstrated some new strategies as depicted in scheme 1. The required starting material was synthesized according to our previous published method [4]. Then, the target compound (2) was prepared from 4-[7-methyl-2-(methylsulfanyl)pyrimido[4,5d][1,3]thiazol-5-yl]morpholine (1) by the treatment of hydrazine hydrate in refluxing ethanol. The treatment of compound (2) with triethylorthoesters gave the corresponding products 3(a-c) and 4(a-b), respectively. Further treatment of compound (2) with monochloroacetone gave quantitatively the desired product (5). The reaction of compound (2) with NaNO2 in H+/H 2 O obtained the azide substitution derivative (6).

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