Synthesis of Lupinine

A synthesis of lupinine (la) is performed from 5-amino-1-pentanol in ten steps. The glutarimide (3) was obtained from 1-(5-hydroxypentyl)-2-(4-methylphenylsulfonyl)acetamide (5) and acrylate (4) via a formal [3+3] annulation. This formation of quinolizidine skeleton was established via a key acid-catalyzed cyclization method.