Amino Acid-Derived <i>trans</i>-<i>N</i>-Chloroformylimidazolidinones: Scalable, Stereoselective Synthesis, Structure, and Utility
作者:Mostafa Mahmoud Amer、Hossay Abas、Daniel J. Leonard、John W. Ward、Jonathan Clayden
DOI:10.1021/acs.joc.9b00727
日期:2019.6.7
N-acyl imidazolidinones, which are key intermediates in the stereoselective synthesis of amino acids by “self-regeneration of stereochemistry” methods, are classically made by only moderately diastereoselective methods. We now report that cyclization of pivaldimino-amides with phosgene in the presence of pyridine may be made fully diastereoselective for the trans-N-chloroformylimidazolidinones, and
Asymmetric and Geometry‐Selective α‐Alkenylation of α‐Amino Acids
作者:Hossay Abas、Josep Mas‐Roselló、Mostafa Mahmoud Amer、Derek J. Durand、Robin R. Groleau、Natalie Fey、Jonathan Clayden
DOI:10.1002/anie.201813984
日期:2019.2.18
Both E‐ and Z‐N′‐alkenyl urea derivatives of imidazolidinones may be formed selectively from enantiopure α‐amino acids. Generation of their enolate derivatives in the presence of K+ and [18]crown‐6 induces intramolecular migration of the alkenyl group from N′ to Cα with retention of double bond geometry. DFT calculations indicate a partially concerted substitution mechanism. Hydrolysis of the enantiopure
.alpha.-Vinyl-.alpha.-aminocarboxylic acids of the general formula: ##STR1## where * indicates a center of asymmetry and R is hydrogen, deuterium, lower alkyl, allyl, benzyl, or benzyl substituted 1 to 3 times by alkyl, alkoxy, fluorine or chlorine and produced enantioselectively from L-methionine by a multistep process.