The first microwave-assisted regiospecific synthesis of 6-substituted pterins

The pyrazine ring was developed in a pyrimidine and in a benzene by Isay type condensations under microwave irradiation to afford pterin and quinoxaline systems. Interestingly, the desired isomerically free 6-substituted pterins including pterin sugar derivatives were synthesised in moderate to good yields whereas mixtures of both 6- and 7-isomers (major) are generally obtained using conventional Isay type condensations.