Resolution of enantiomers of novel C2 -symmetric aminobisphosphinic acids via diastereomeric salt formation with quinine.

C2 -symmetric N,N-bis(phosphinomethyl)amines were prepared by the thermal reaction of aromatic aldehydes with ammonia and hypophosphorus acid as previously described. Both enantiomers of C2 -symmetric N,N-bis(phosphinomethyl)amine were obtained in a high enantiomeric purity through the diastereomeric salt formation with (-)-quinine, and subsequent fractional crystallization. X-ray crystallographic analysis of one of the diastereomeric salts clearly revealed that (-)-quinine could be an efficient resolving agent for obtaining the single enantiomer (R,R)-N,N-bis(phosphinomethyl)amine.