Leguminosae alkaloids. VII. Synthesis of (+)-lamprolobine

α,β-Unsaturated Nitriles: Stereoselective Conjugate Addition Reactions

“…Equilibration resulted in the exclusive formation of 9a (Scheme ). This equilibration is in stark contrast to analogous reactions of quinolizidine esters that result in the ester adopting an equatorial orientation . We interpret the preference for an axial nitrile substituent as arising from a very small nitrile−proton syn−axial interaction rather than a less favorable gauche interaction with the adjacent methylene in 9b…”

Influence of ring size on the reduction of vinylogous urethanes. Applications to the synthesis of lupinine and epilupinin

“…Less drastically, Goldberg and Lipkin accomplished epimerisation in unspecified yield by heating the lupinate ester 14 with sodium ethoxide in ethanol. 20 We found that stereoselective cis-hydrogenation of the bicyclic vinylogous urethane 6 could be accomplished under far milder conditions than those employed by Lhommet's group. Hydrogenation over Adams catalyst in absolute ethanol at a hydrogen pressure of 5 atm afforded (±)-ethyl lupinoate 14 as the sole detectable isomer in a yield of 83% (Scheme 3).…”

“…When the reactants were heated in a 2:1 mixture of toluene and acetonitrile, the intermediate iodide cyclised spontaneously to give the 3,4,6,7,8,9-hexahydro-2H-quinolizine 6 in 74% yield. Although other workers have prepared compound 6 by different routes, 11,20,21 characterisation has hitherto been sketchy and 13 C NMR data have not previously been reported.…”