Exploring an Alternative Synthetic Pathway for the Total Synthesis of (±)-Nordasycarpidol and (±)-Nordasycarpidone

A total synthesis of the strychnos alkaloids, dasycarpidol and nordasycarpidone, has been accomplished from 2-(3-ethyl-1-oxo-2,3,4,9-tetrahydro-1H-carbazol-2-yl)acetonitrile 1, which is the C-2 ethyl side chain of carbazole as well as carbazole-fused lactone 3 that is conveniently of the key azocino[4,3-b]indole skeleton 6. These syntheses of the target natural products are accomplished without a protecting group, which has a carbonyl group at the C-1 position of the carbazole. These alternative routes are accomplished by shortening the number of steps with high efficiency and also nordasycarpidol 8 synthesized for the first time in the literature. The structures of all the presently synthesized compounds were confirmed using spectroscopic methods (FT-IR, H-1 NMR, C-13 NMR).