New approach to the synthesis of biologically active derivatives of pyranocoumarins

Operationally simple and convenient synthesis of selectively protected derivatives of 5,7-dihydroxycoumarins was proposed. The proposed method is based on the reaction of the coumarins with nicotinoyl azide yielding 7-nicotinoyloxy derivatives of the coumarins. This approach can significantly improve the procedure for preparing the dimethylpyranocoumarins, an important semiproduct for synthesis of anti-HIV agents.