1408318-39-7Relevant articles and documents
α-Amino Acids and α,β-Dipeptides Intercalated into Hydrotalcite: Efficient Catalysts in the Asymmetric Michael Addition Reaction of Aldehydes to N-Substituted Maleimides
Landeros, José M.,Cruz-Hernández, Carlos,Juaristi, Eusebio
, p. 5117 - 5126 (2021)
In this work, a series of α-amino acids (L-Phe, D-Phe, L-Trp) and several α,β-dipeptides (H2N-L-Val-N-Bn-β-Ala-COOH and H2N-L-Leu-N-Bn-β-Ala-COOH) intercalated into hydrotalcite (Mg/Al, x=0.333) were prepared by high speed ball milling (HSBM) assisted rehydration/reconstruction methods, followed by sonication and mechanical stirring. All organic-inorganic hybrid samples were characterized by powder X-ray diffraction (XRD) and FTIR-ATR spectroscopy. The catalytic activity of the resulting hydrotalcite-supported materials (natural and hybrid) was evaluated in the asymmetric Michael addition reaction of α,α-disubstituted-aldehydes to N-substituted-maleimides. Pristine (HTS), calcined (HTC) and water-reconstructed (HTR-l) hydrotalcite-derived materials exhibited very low catalytic activities, affording racemic mixtures of the anticipated Michael adduct. By contrast, hybrid materials showed better activities, especially HTR-α-amino acid catalysts afforded Michael products in up to 94 % yield and with rather high enantioselectivity (enantiomeric ratio (e.r.) up to 99 : 1) at room temperature under neat reaction conditions. The effect of solvents and Br?nsted basic or acidic additives was evaluated using the best hybrid catalyst, HTR-L-Phe. In addition, recycling and reuse of the catalyst (up to 4 cycles) and large-scale experiments was successfully carried out.
Solution-phase synthesis of novel seven-membered cyclic dipeptides containing α- And β-amino acids
Jimenez-Gonzalez, Erika,Gabriela Avila-Ortiz, C.,Gonzalez-Olvera, Rodrigo,Vargas-Caporali, Jorge,Juaristi, Eusebio,Dewynter, Georges
, p. 9842 - 9852,11 (2020/08/20)
A convenient synthetic procedure for the preparation of seven-membered cyclic α,β-dipeptides is described. Following coupling of N-protected α-amino acids with N-substituted β-amino acid tert-butyl esters, that affords linear α,β-dipeptides, the protecting groups at the terminal functionalities were removed and the open-chain dipeptides were cyclized with phenylphosphonic dichloride, PhP(O)Cl2, to give the desired cyclic α,β-dipeptides in good yields. NMR studies, X-ray diffraction analysis, and DFT calculations provided evidence for the conformation adopted by these cyclic dipeptides in solution, in the solid-state, and in the gas phase.
