Synthetic studies on lythraceae alkaloids. II. The mannich reaction of isopelletierine with 3-methoxybenzaldehyde and 3-hydroxybenzaldehyde.

Abstract

The Mannich reaction of isopelletierine (III) with 3-methoxybenzaldehyde (VI) in aqueous sodium hydroxide afforded the trans- and cis-quinolizidine (VIII and IX) in the 1 : 6 ratio, whereas the reaction with 3-hydroxybenzaldehyde (VII) gave almost exclusively the trans-quinolizidine (X). On the other hand, the reaction with VI in methanol afforded VIII and IX in the 6 : 1 ratio. On the basis of the detailed experiments the Mannich reaction of III with arylaldehyde under an alkaline condition was found to afford at first cis-4-arylquinolizidin-2-one, which then isomerized into the corresponding trans-isomer. And the stereoselectivity of this reaction was found to depend on solvents, solubilities of the starting arylaldehydes and products, and reaction times.