Synthesis of a new heterocyclic system: pyrimidine structural analogues of natural integrastatins A, B

In this paper for the first time we report simple one-step synthesis of 5-methyl-11,12-dihydro-5H-5,11-epoxybenzo[7,8]oxocino[4,3-d]pyrimidine derivatives by acid-catalyzed cyclization reaction of various 4-methyl-5-acetyl pyrimidine derivatives with salicylic aldehyde. It was shown that 2-substituted 4-methyl-5-acetylpyrimidines successfully react to form a cyclization product. At the same time, 4-methyl-5-acetylpyrimidines with a substituent in the 6th position do not enter into the cyclization reaction. This may be caused by the negative effect of substituents in the 6th position, which hinder the free rotation of the acetyl group and prevent the formation of a stable pre-reaction complex. The structure of the obtained 5-methyl-11,12-dihydro-5H-5,11-epoxybenzo[7,8]oxocino[4,3-d]pyrimidine derivatives was confirmed using 1H, 13C spectroscopy, mass spectrometry and X-ray diffraction analysis.