Purified ergopeptine alkaloids are often used in studies related to tall fescue toxicosis without regard to epimerization that occurs when ergopeptines are solvated. The objectives of this study were to measure the rates of alpha-ergocryptine epimerization to alpha-ergocryptinine at room temperature and at -40 degrees C, and to measure the rate of ergovaline epimerization to ergovalinine at 37 ...

Peptides were produced in high yields and, if any, very low epimerization, by mechanochemical coupling of peptide fragments containing highly epimerization-prone and/or hindered amino acids at C-term. Ball milling was clearly identified as the key element enabling one to obtain such results.

Abstract Epimerization can change the catechin content and composition of samples during extraction analytical analyses. To control effect epimerization, we developed a novel stable isotope dilution liquid chromatography-mass spectrometry (LC–MS) method using catechin-2,3,4- 13 C 3 epicatechin-2,3,4- as stable-isotope-labeled internal standards (SIL-ISs). When SIL-ISs were used, epicatechin con...

The observed epimerization at C2 in the Horner-Wadsworth-Emmons (HWE) reaction of chiral 2-substituted-4-oxopiperidines has been investigated and, on the basis of the experimental results, a mechanism for this unexpected process has been proposed.

Continuous in situ generation of phosgene and its use in acid chloride formation in a microflow system were demonstrated. The acid chloride was subsequently coupled with an amine in high yield without severe epimerization.

A recently proposed model of non-autocatalytic reactions in dipeptide formation that leads to spontaneous symmetry breaking and homochirality was examined. The model is governed by activation, polymerization, epimerization, and depolymerization of amino acids. Symmetry breaking was determined to result primarily from the different rates of reactions that involve homodimers and heterodimers, i.e...

An efficient and environmentally friendly methodology for the solvent-free synthesis of α-amino nitrile derived ureas from α-amino acid based amino nitriles has been developed. At room temperature no epimerization was observed in the resulting ureas, but under microwave heating, epimerization occurred at the chiral center bearing the cyano group.