Boc-phenylglycine:: The reagent of choice for the assignment of. The absolute configuration of α-chiral primary amines by 1H NMR spectroscopy

The absolute configuration of an alpha-substituted primary amine can be easily determined by direct comparison of the H-1 NMR spectra of the (R)- and the (S)-Boc-phenylglycine derivatives. A simplified model, based on extensive conformational analysis and NMR data, is presented that associates the spatial location of the substituents around the asymmetric carbon of the amine with the signs of Delta delta(R,S). The substituent with a negative Delta delta(R,S);occupies the position of L-1 in Figure 7 and that with a positive Delta delta(R,S) the position of LB From this model the absolute configuration (RIS) of the chiral center can be determined. The BPG amides give rise to much higher Delta delta(R,S) values than the classical reagents MTPA and MPA and offer a greater guarantee for the correct assignment of the absolute configuration.