The Papilionaceous Alkaloids: Xvii. The Synthesis of Structural Isomers of Sparteine

A structural isomer of sparteine, Ψ-sparteine, has been synthesized from 2,2′-dipyridylmethane which was condensed via its lithium salt with β-bromomethylmalonic ester, followed by fission of the ether link. The product of the condensation, αα-di(2-pyridyl)-γγ-dicarbethoxy-propane, was reduced catalytically to the corresponding dipiperidyl compound which on heating in vacuo readily lost ethanol, giving rise to two isomeric dilactams. Each dilactam was reducible to a different isomer of sparteine. Just like sparteine, Ψ-sparteine can exist in three stereoisomeric forms, two of which, however, are internally compensated and therefore not resolvable.