Abstract (1′ S, 5R, S)-(1′-phenyleth-1′-yl)-5-iodomethyl-imidazolines 4a, b have been synthesised and easily resolved by silica gel chromatography. The correlation between the configuration and the 1 H NMR chemical shifts allows to assign the configuration at the C-5 of these intermediates. Each pure diastereomer has been converted to R (−)-and to S (+)-1, 2-propyldiamine, respectively.