10419-67-7Relevant articles and documents
Chiral permselectivity in nanoporous opal films surface-modified with chiral selector moieties
Cichelli, Julie,Zharov, Ilya
, p. 1870 - 1875 (2007)
The chiral permselectivity in thin opal films modified on the silica surface with chiral selector moieties was studied as a function of opal film geometry, supporting electrolyte concentration, solvent polarity, and chiral selector and linker structure. While opal film thickness, supporting electrolyte concentration and linker length and structure did not have a significant influence on the chiral permselectivity, the nanopore size, solvent polarity and selector structure had a pronounced effect. These observations are in agreement with the chiral selectivity mechanism in the opal films in which the permeating enantiomers are transported with different rates through the surface utilizing non-covalent interactions between the chiral permeant molecules and surface-bound chiral selectors. The chiral selectivity (transport rate ratio for S and R enantiomers) achieved in the present study was 4.5, which is one of the highest reported for chiral membranes. The Royal Society of Chemistry 2007.
Enantioselective radical C–H amination for the synthesis of β-amino alcohols
Nakafuku, Kohki M.,Zhang, Zuxiao,Wappes, Ethan A.,Stateman, Leah M.,Chen, Andrew D.,Nagib, David A.
, p. 697 - 704 (2020/07/02)
Asymmetric, radical C–H functionalizations are rare but powerful tools for solving modern synthetic challenges. Specifically, the enantio- and regioselective C–H amination of alcohols to access medicinally valuable chiral β-amino alcohols remains elusive. To solve this challenge, a radical relay chaperone strategy was designed, wherein an alcohol was transiently converted to an imidate radical that underwent intramolecular H-atom transfer (HAT). This regioselective HAT was also rendered enantioselective by harnessing energy transfer catalysis to mediate selective radical generation and interception by a chiral copper catalyst. The successful development of this multi-catalytic, asymmetric, radical C–H amination enabled broad access to chiral β-amino alcohols from a variety of alcohols containing alkyl, allyl, benzyl and propargyl C–H bonds. Mechanistic experiments revealed that triplet energy sensitization of a Cu-bound radical precursor facilitates catalyst-mediated HAT stereoselectivity, enabling the synthesis of several important classes of chiral β-amines by enantioselective, radical C–H amination. [Figure not available: see fulltext.]
Dynamic Kinetic Resolution of N-Protected Amino Acid Esters via Phase-Transfer Catalytic Base Hydrolysis
Yamamoto, Eiji,Wakafuji, Kodai,Furutachi, Yuho,Kobayashi, Kaoru,Kamachi, Takashi,Tokunaga, Makoto
, p. 5708 - 5713 (2018/05/30)
Asymmetric base hydrolysis of α-chiral esters with synthetic small-molecule catalysts is described. Quaternary ammonium salts derived from quinine were used as chiral phase-transfer catalysts to promote the base hydrolysis of N-protected amino acid hexafluoroisopropyl esters in a CHCl3/NaOH (aq) via dynamic kinetic resolution, providing the corresponding products in moderate to good yields (up to 99%) with up to 96:4 er. Experimental and computational mechanistic studies using DFT calculation and pseudotransition state (pseudo-TS) conformational search afforded a TS model accounting for the origin of the stereoselectivity. The model suggested π-stacking and H-bonding interactions play essential roles in stabilizing the TS structures.
Direct synthesis of amides from coupling of alcohols and amines catalyzed by ruthenium(II) thiocarboxamide complexes under aerobic conditions
Sindhuja, Elangovan,Ramesh, Rengan,Balaji, Sundarraman,Liu, Yu
, p. 4269 - 4278 (2014/12/09)
Four octahedral ruthenium(II) thiocarboxamide complexes of the general formula [RuClCO(AsPh3)2(L)] (L = N-substituted pyridine-2-thiocarboxamide) incorporating carbonyl and triphenylarsine have been synthesized from the reaction of 1 equiv of ruthenium precursor [RuHClCO(AsPh3)3] with 1 equiv of thiocarboxamide ligands in refluxing ethanol in the presence of base. All the new complexes have been fully characterized by means of elemental analysis, IR, UV-vis, and NMR spectral methods. Molecular structures of all the complexes were determined by X-ray crystallography, which confirm the coordination mode of thiocarboxamide and reveal the presence of a distorted octahedral geometry around the Ru ion. All the ruthenium(II) thiocarboxamide complexes were generated as highly efficient catalysts for synthesis of secondary or tertiary amides by coupling of amines and alcohols with low catalyst loading, and the maximum yield was obtained up to 97%. The coupling reaction can be readily carried out under mild aerobic conditions, and release of water is the only byproduct. Further, the effect of substituents of the ligand, solvents, reaction temperature, time, and catalyst loading on the catalytic activity of the complexes has been investigated. A plausible mechanism is proposed for the synthesis of amides via hemiaminal as intermediate through an oxidation of an alcohol to aldehyde.
Combining Magnetic Resonance Spectroscopies, Mass Spectrometry, and Molecular Dynamics: Investigation of Chiral Recognition by 2,6-di-O-Methyl-β-cyclodextrin
Franchi, Paola,Lucarini, Marco,Mezzina, Elisabetta,Pedulli, Gian Franco
, p. 4343 - 4354 (2007/10/03)
EPR spectroscopy has been employed to investigate the formation of complexes between heptakis-(2,6-O-dimethyl)-β-cyclodextrin (DM-β-CD) and different enantiomeric pairs of chiral nitroxides of general structure PhCH2N(O·)CH(R)R′. Accurate equilibrium measurements of the concentrations of free and included radicals afforded the binding constant values for these nitroxides. The relationship between the stereochemistry of the DM-β-CD complexes and the thermodynamics of complexation was elucidated by correlating EPR data with 1H-1H NOE measurements carried out on the complexes between DM-β-CD and the structurally related amine precursors of nitroxides. NOE data suggested that inclusion of the stereogenic center in the DM-β-CD cavity occurs only when the R substituent linked to the chiral carbon contains an aromatic ring. For these types of complexes, molecular dynamics simulation indicated that the depth of penetration of the stereogenic center into the cyclodextrin cavity is determined by the nature of the second substituent (R′) at the asymmetric carbon and is responsible for the observed chiral selectivity. Analysis of mass spectra showed that, for the presently investigated amines, electrostatic external adducts of CDs with protonated amines are detected by ESI-MS.
Novel enantioselective synthesis of both enantiomers of furan-2-yl amines and amino acids
Demir, Ayhan S.,Sesenoglu, Oezge,Uelkue, Dincer,Arici, Cengiz
, p. 91 - 105 (2007/10/03)
A new enantioselective synthesis of furan-2-yl amines and amino acids is described, in which the key step is the oxazaborolidine-catalyzed enantioselective reduction of O-benzyl (E)- and (Z)-furan-2-yl ketone oximes to the corresponding chiral amines. The chirality of the furan-2-yl amines is fully controlled by the appropriate choice of the geometrical isomer of the O-benzyl oxime. Oxidation of the furan ring furnished amino acids in high yields.
Beauveria bassiana ATCC 7159 contains an L-specific α-amino acid benzamidase
Holland, Herbert L.,Andreana, Peter R.,Salehzadeh-Asl, Reza,Van Vliet, Aaron,Ihasz, Nancy J.,Brown, Frances M.
, p. 667 - 672 (2007/10/03)
Biotransformation of a series of racemic N-benzoyl α-amino acids by the fungus Beauveria bassiana ATCC 7159 results in isolation of the corresponding D-amino acid benzamides in high enantiomeric purity and yield.
Synthesis of (S)- and (R)-1-(2-furyl)alkylamines and (S)- and (R)-α- amino acids through the addition of organometallic reagents to imines derived from (S)-Valinol
Alvaro, Giuseppe,Martelli, Gianluca,Savoia, Diego,Zoffoli, Andrea
, p. 1773 - 1777 (2007/10/03)
(S)-1-(2-Furyl)alkylamines were prepared through the addition of organometallic reagents to the imine derived from 2-furaldehyde and (S)- valinol, previous protection of the auxiliary hydroxy group as trimethylsilyl ether, followed by removal of the auxiliary. Then, protection of the primary amine as tosylamide or benzamide and oxidation of the furan ring gave the N- derivatives of (S)-α-amino acids. (R)-N-Benzoylphenylglycine was prepared from the benzaldimine, where the hydroxy group was protected as the tert- butyldimethylsilyl ether, through addition of 2-furyllithium.
CHEMO-ENZYMATIC ASYMMETRIC SYNTHESIS OF AMINO ACIDS. ENANTIOSELECTIVE HYDROLYSES OF 2-PHENYL-OXAZOLIN-5-ONES.
Gu, Rui-Lin,Lee, Ik-Soo,Sih, Charles J.
, p. 1953 - 1956 (2007/10/02)
Porcine pancreatic lipase and the lipase of Aspergillus niger catalyze the enantioselective hydrolysis of a series of 4-substituted-2-phenyl-oxazolin-5-ones to yield optically active (S)- and (R)-N-benzoyl amino acids respectively.
