Conformational effects in reversed-phase liquid chromatographic separation of diastereomers of cyclic dipeptides

Article abstract of DOI:10.1021/ac00062a010

The capacity factors, k′, of 11 cyclic dipeptides (X-Y) including diastereomers have been determined on an RP-HPLC column in 30% and 50% methanol and 10%, 30%, and 50% acetonitrile solutions. These factors are roughly correlated with hydrophobic parameters, such as octanol-water partition coefficients estimated and k′ values for alcohols. For a pair of diastereomers of cyclic (L-X-L-Phe) and (L-X-D-Phe) derivatives k′_LL is larger than k′_LD and for cyclic (D-Ala-L-Trp) and (L-Ala-L-Trp) k′_LL is smaller than k′_DL, particularly in highly aqueous solutions. These elution orders can be well predicted by the holistic molecular surface area approach which takes into account the folded structures of cyclic dipeptides. The present results will be useful for prediction of the log k′ values of larger peptides and the hydrophobicity and related properties of peptides.