While direct Sonogashira coupling of 6-halopurines with methyl propiolate and with propargyl aldehyde was not successful, the corresponding orthoester and propargyl aldehyde diethylacetal reacted smoothly. Such prepared orthoester was then converted to the desired methylester by methanolysis, the acetal was too stable to be hydrolyzed. The obtained 6-ethynylpurines, bearing orthoester, acetal, methoxycarbonyl and for comparison also the phenyl substituent on the ethynyl group, were subjected to the cycloaddition reaction with cyclopentadiene, diazomethane and phenylazide. Electron deficient alkynylpurines were considerably more reactive in this reaction compared to the not activated phenylethynyl derivative. The prepared alkynylpurines exhibited medium cytostatic activity (IC50 = 2.6–15 μM), while the cycloadducts were inactive.
直接的Sonogashira偶联反应无法成功地将6-卤代嘌呤与丙烯酸甲酯和丙炔醛偶联,但相应的orthoester和丙炔醛二乙醇缩醛却能顺利反应。制备的orthoester随后通过甲醇解反应转化为所需的甲酯,而缩醛却过于稳定而无法水解。所得的6-乙炔基嘌呤,带有orthoester、缩醛、甲氧羰基和为了比较而添加的苯基取代基,被用于与环戊二烯、重氮甲烷和苯基叠氮化物进行环加成反应。与未活化的苯基乙炔衍生物相比,电子不足的炔基嘌呤在这个反应中表现出更高的反应性。制备的炔基嘌呤表现出中等的细胞毒素活性(IC50=2.6-15μM),而环加成产物则无活性。