Total syntheses of (-) epilupinine and (-)-tashiromine using imino-aldol reactions.

Short routes to enantiomerically pure indolizidine and quinolizidine alkaloids have been developed using imino-aldol reactions of enolates derived from phenyl 5-chlorovalerate. High levels of syn selectivity (dr ∼13–16:1) were obtained using lithium enolates of phenyl esters in combination with tert-butylsulfinyl imines. The imino-aldol adducts were deprotected and cyclized to afford (−)-epilupinine ((−)-2) and (−)-tashiromine ((−)-1) in two further steps.