Chromatographic behaviour of diastereoisomers : VI. Relative retentions of the diastereoisomers of 3-hydroxy-2,3-diarylpropionates on silica gel and their theoretical interpretation

Abstract

Separations by thin-layer chromatography on silica gel have been achieved for fifteen diastereoisomeric pairs of the type Ar—CH(X)—CH(COOR)—Ar′ (X = OH, OAC or NHPh; R = Me, iso-Pr, n-Bu, iso-Bu or tert.-Bu) which have known relative configurations. R F values of the compounds studied have been measured as a function of the concentration of diethyl ether in mixtures with heptane. Thus, the values of a parameter, related to the adsorption pattern, have been found. The relative retentions of the diastereoisomers R F ( erythro ) > R F ( erythro ) within those compounds where X = OH and R - tert.-Bu have been explained. Four different patterns of adsorption have been discussed. The data and the conclusions permit further outlining of the scope of each of the two retentions; they also support the previously elaborated criteria for thin-layer chromatographic assessment of the relative configurations of other diastereoisomeric pairs of tetrasubstituted ethanes.