Stereocomplexity and stereoselective synthesis of triamine molecules bearing four chiral carbon centers: Stereodifferentiated preparation of all 10 stereoisomers of 2,6-bis[1-(1-phenylethylamino)ethyl]pyridines.

Compounds (S,S)-2,6-bis(1-hydroxyethyl)pyridine, (R,R)-2,6-bis(1-acetoxyethyl)pyridine, and (1R,1'S)-2-(1-acetoxyethyl)-6-(1'-hydroxyethyl)pyridine were obtained by lipase-catalyzed kinetic acetylation of 2,6-bis(1-hydroxyethyl)pyridine as enantiomerically pure forms. The stereospecific replacement of hydroxy groups with (R)-phenylethylamine or (S)-phenylethylamine via its methanesulfonate or toluenesulfonate simultaneously or stepwise afforded all the stereoisomers of 1. Stereospecific preparation of all the 10 possible stereoisomers of 2,6-bis[1-(1-phenylethylamino)ethyl]pyridines 1a-f was achieved. Triamine 1b reacted with ZnCl2 to form Zn-triamine complex 16, the structure of which was determined by X-ray crystallographic analysis.