Nonracemic Betti Base as a New Chiral Auxiliary:  Application to Total Syntheses of Enantiopure (2<i>S</i>,6<i>R</i>)-Dihydropinidine and (2<i>S</i>,6<i>R</i>)-Isosolenopsins

Total syntheses of enantiopure alkaloidal natural products (2<i>S</i>,6<i>R</i>)-dihydropinidine (as hydrochloride) and (2<i>S</i>,6<i>R</i>)-isosolenopsins (as hydrochlorides) were achieved in four steps and in 80−82% total yields by using a synthetic strategy of the formation-cleavage of 1,3-oxazinane. (<i>S</i>)-Betti base was proved to be an excellent chiral auxiliary and a novel Pd/C catalyzed <i>N</i>-debenzylation straightforward to amine hydrochloride was developed in the presence of CH<sub>2</sub>Cl<sub>2</sub>.