Simple and highly efficient preparation and characterization of (−)-lupanine and (+)-sparteine

In a simple and convenient way, we have improved the non-chromatographic isolation of optically pure (−)-2-oxosparteine ((−)-lupanine) and (+)-sparteine. The fast and efficient method for the determination of the ee of bisquinolizidine alkaloids has been proposed. A relatively simple simple 1H NMR method has been applied for evaluation of the % ee of enantiomers of the lupanines and sparteines with the chiral dibenzoyltartaric acids as the shift reagents. The 1H NMR spectra of the bases and the new salts in polar solvents have been measured. The results are confirmed by chiral HPLC method. Additionally, for the first time X-ray analysis of the salt of (−)-lupanine has been performed. The improved method of purification of bisquinolizidine alkaloids will considerably facilitate the employment of these alkaloids as chiral ligands in asymmetric reactions and as pharmacological tools