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-tetrahydro-2H-pyrano(3,2-c)quinolin-5-one.