Two-Component Method to Enantiopure Quinolizidinones and Indolizidinones. Total Synthesis of (−)-Lasubine II

The reaction of iodides 1 and enantiopure beta-amino esters 2 mediated by potassium carbonate in acetonitrile at 65 degrees C provides quinolizidinones or indolizidinones 3, together with piperidines or pyrrolidines 4. Hydrolysis of 4 to the corresponding carboxylic acids followed by treatment of acetic anhydride/triethylamine gives 3 in high yields. Using 3a as a key intermediate, (-)-lasubine II is synthesized in four steps. [reaction: see text]