Synthesis of Pyrano[3,2-c]quinolin-5-one Alkaloids: Veprisine, 7-Dimethylallyloxy-N-methylflindersine and cis-3,4-Dihydroxy-7-methoxy-2,2,6-trimethyl-3,4,5,6-tetr ahydro-2H-pyrano[3,2-c]quinolin-5-one

Abstract

Condensation of the appropriate 4-hydroxyquinolin-2-ones with 3-methylbut-2-enal gave pyrano[3,2-c]quinolin-5-ones which were further elaborated to the three alkaloids named in the title.