Total synthesis of the putative structure of the lupin alkaloid plumerinine.

[reaction: see text]. A stereocontrolled synthesis of quinolizidine 1, the reported structure of plumerinine, has been accomplished in 10 steps from 4-methoxypyridine. The key step is a highly facial selective intramolecular [2 + 2] photocycloaddition of a 2,3-dihydro-4-pyridone. The reported spectral data for plumerinine did not match that of our synthetic 1.