Investigation of the diastereoselective Mannich reaction using imidazolidin-2-thione as a chiral auxiliary
摘要:
Titanium mediated asymmetric Mannich reactions using imidazolidin-2-thione as a chiral auxiliary proceeded in good yields and with high diastereoselectivity to afford the anti-products in the presence of PPh3 additive. A non-chelated transition state with the PPh3-bound titanium enolate was proposed to explain the stereochemistry of the product. Alcoholysis of the adducts with methanol cleaved the imidazolidin-2-thione auxiliary to give the methyl esters in good yields and with excellent ee values. (C) 2014 Elsevier Ltd. All rights reserved.
Traceless Approach for the Synthesis of 3,5-Disubstituted Thiohydantoins on Functionalized Ionic-Liquid Support
摘要:
A traceless approach for the synthesis of 3,5-disubstituted thiohydantoins on a novel functionalized ionic-liquid support, 5, is described. Acylation of benzylamine functionalized ionic-liquid support with amino acids yielded ionic-liquid-supported amino acids, which reacted with isothiocyanates to afford ionic-liquid-supported thioureas. Following intramolecular cyclization cleavage from the ionic-liquid support by trifluoroacetic acid (TFA), the desired 3,5-disubstituted thiohydantoins were obtained in good yields and purities. The efficiency of this ionic-liquid-phase strategy facilitated isolation and analysis of intermediates and removal of excess reagents and by-products during the reaction process.
tetrapeptide spacer arm for the rate of lysosomal enzymatic release of PQ can be possible. A third group, comprising epsilon-aminocaproic acid-PQ derivatives which lack a free alpha-amino group, was synthesized. This was done to study the importance of enzymes, other than aminopeptidases, during lysosomaldegradation of these derivatives. To allow HPLC analysis of the pattern of degradation of tetrapeptide-PQ
Pavlik, Manfred; Kluh, Ivan; Pavlikova, Frantiska, Collection of Czechoslovak Chemical Communications, 1989, vol. 54, # 7, p. 1940 - 1954
作者:Pavlik, Manfred、Kluh, Ivan、Pavlikova, Frantiska、Vasickova, Sona、Kostka, Vladimir
DOI:——
日期:——
Simple and Efficient Synthesis of 5-Substituted-3-phenyl-2-thioxoimidazolidin-4-one Derivatives from<i>S</i>-Amino Acids and Phenylisothiocyanate in Et<sub>3</sub>N/DMF-H<sub>2</sub>O
作者:Asha D. Jangale、Yogesh B. Wagh、Yogesh A. Tayade、Dipak S. Dalal
DOI:10.1080/00397911.2015.1052506
日期:2015.8.18
A concise approach for the transformation of various S-amino acids into the 5-alkyl-3-phenyl-2-thioxoimidazolidin-4-one heterocycles using phenylisothiocyanate is described. Phenylthiohydantoins of amino acid were synthesized at room temperature in Et3N/DMF-H2O with easy workup and excellent yields.
CHEN, TENG-MAN;COUTANT, JOHN E., J. CHROMATOGR., 463,(1989) N, C. 95-106
作者:CHEN, TENG-MAN、COUTANT, JOHN E.
DOI:——
日期:——
BOUDAH, F.;GUERMOUCHE, M. H., ANALUSIS, 18,(1990) N, C. 483-486