CHIRAL PURITY DETERMINATION OF TOBACCO ALKALOIDS AND NICOTINE-LIKE COMPOUNDS BY H-1-NMR SPECTROSCOPY IN THE PRESENCE OF 1,1'-BINAPHTHYL-2,2'-DIYLPHOSPHORIC ACID

The enantiomeric purity of several tobacco alkaloids and nicotine-like com pounds was determined using H-1 NMR (300 MHz) spectroscopy in the presence of (-)-(R)-1,1'-binaphthyl-2,2'-diylphosphoric acid (BNPPA) as a chiral complexing agent. The most significant signal splitting re sulting horn diastereoisomeric complexation are seen for chemical shif ts in the proximity of the pyridinyl nitrogen. Chemical shift data exc lude any contribution of the pyrrolidinyl protons to chiral recognitio n, but when the pyrrolidine ring is replaced by a piperidine ring, i.e ., for compounds such as rac-anabasine and rac-anatabine, non-equivale nce between enantiomers was observed for protons close to the piperidi ne ring. A new approach for the preparation of the pure (-)-(S)- and ( +)-(R)-enantiomers of nornicotine, a tobacco alkaloid and metabolite o f nicotine, was developed. The optically pure enantiomers thus obtaine d were used to establish the minimum sensitivity of the NMR spectrosco pic method of chiral analysis. These findings provide a new, general, and facile method for the determination of enantiomeric purity of toba cco alkaloids and nicotine-like compounds. (C) 1996 Wiley-Liss, Inc.