“…In addition, pyrimidine derivatives such as pyrazolo [1,5-a]pyrimidine, pyrido [2,3-d]pyrimidine, thieno [2,3-d]pyrimidines, pyrrolo [2,3-d]pyrimidines, and indolylpyrimidines showed potent antitumor [15][16][17][18][19][20], antitubercular [21], anti-inflammatory [22], and antidiabetic [23] activities. On the basis of the reported observations and in continuation of our ongoing interest in the synthesis of biologically active molecules [27][28][29][30], the present work describes the synthesis of new series of thiazolo [3,2-a]pyrimidine and pyrimido [2,1-b] [1,3] thiazine derivatives as well as the evaluation of their antibacterial and antifungal activities. On the basis of the reported observations and in continuation of our ongoing interest in the synthesis of biologically active molecules [27][28][29][30], the present work describes the synthesis of new series of thiazolo [3,2-a]pyrimidine and pyrimido [2,1-b] [1,3] thiazine derivatives as well as the evaluation of their antibacterial and antifungal activities.…”