Total synthesis of the tetracyclic lupin alkaloid (+)-allomatrine.

(+)-Allomatrine (1) has been synthesized using an imino-aldol reaction and N-acyliminium cyclization as key steps. Strategically, use of the tert-butylsulfinimine derivative of (E)-4-(trimethylsilyl)but-2-enal enabled the staged formation of three C-C bonds, a C-N bond, and the four stereogenic centers within the target.