Complexation equilibrium in a substrate- MgCl2(CaCl2)-Pd/C catalytic system and the influence of its position on asymmetric induction in hydrogenation ofN-acetyl-dehydrophenylalanyl-S-proline
作者:I. N. Lisichkina、A. I. Vinogradova、L. N. Kurkovskaya、M. B. Saporovskaya、V. M. Belikov、T. Yu. Vasil'eva
DOI:10.1007/bf01457764
日期:1996.8
The role of Ca and Mg salts as promoters of asymmetricinduction in hydrogenation ofN-acetyl-dehydrophenylalanyl-S-proline in a substrate— MX2—Pd/C catalytic system was studied. The data of potentiometric titration,1H NMR spectroscopy, and the value of diastereomeric excess (de) of the resultingN-acetyl-R-phenylalanyl-S-proline indicate the complexation of the substrate with calcium and magnesium chlorides
作者:I. N. Lisichkina、A. G. Ivanova、A. S. Peregudov、V. M. Belikov
DOI:10.1023/a:1011397803696
日期:——
The peptide protons in N-acetyl -alpha,beta -dehydrodipeptides (DHDP) dissociate in aqueous methanol in the presence of magnesium salts upon the addition of alkali, which favors the diastereoselectivities of their hydrogenation over Pd/C. By contrast, the N-H bonds of the N-acetyl groups in DHDP seem not to dissociate under these conditions. The dissociation of the peptide N-H bonds in strongly alkaline solutions was studied by F-19 NMR spectroscopy for model compounds containing the 4-FC6H4 fragment.
Complexation as the driving force in diastereoselective hydrogenation of dehydrodipeptides