Synthesis of 2-substituted 9-oxa-guanines {5-aminooxazolo[5,4-d]pyrimidin- 7(6H)-ones} and 9-oxa-2-thio- xanthines {5-mercaptooxazolo[5,4-d]pyrimidin- 7(6H)-ones}

• Subrata Mandal,
• Wen Tai Li,
• Yan Bai,
• Jon D. Robertus and
• Sean M. Kerwin

Beilstein J. Org. Chem. 2008, 4, No. 26, doi:10.3762/bjoc.4.26

• -dihydroxypyrimidine (1a) [19] (Figure 2). Unfortunately, for other 5-acylamino analogs of 1a, this route failed to afford the required oxazolo[5,4-d]pyrimidines, presumably due to decomposition of the product at the temperatures required for cyclodehydration. Other cyclodehydration conditions (POCl3, PPA) were also