The conformations of four β-amino acids in a model peptide environment were investigated using Hartree-Fock (HF) and density functional theory (DFT) methods in gas phase and with solvation. Initial structures were ob...The conformations of four β-amino acids in a model peptide environment were investigated using Hartree-Fock (HF) and density functional theory (DFT) methods in gas phase and with solvation. Initial structures were obtained by varying dihedral angles in increments of 45° in the range 0° - 360°. Stable geometries were optimized at both levels of theory with the correlation consistent double-zeta basis set with polarization functions (cc-pVDZ). The results suggest that solvation generally stabilizes the conformations relative to the gas phase and that intramolecular hydrogen bonding may play an important role in the stability of the conformations. The β3 structures, in which the R-group of the amino acid is located on the carbon atom next to the N-terminus, are somewhat more stable relative to each other than the β2 structures which have the R-group on the carbon next to the carbonyl.展开更多
A series of novel homochiral β-oligopeptides bearing aryl side chains was designed and synthesized from （S）-β-phenyl-β-amino acid derivatives by solution-phase methods. By means of circular dichroism（CD）, Fouri...A series of novel homochiral β-oligopeptides bearing aryl side chains was designed and synthesized from （S）-β-phenyl-β-amino acid derivatives by solution-phase methods. By means of circular dichroism（CD）, Fourier- transform infrared spectrometry（FTIR）, powder X-ray diffraction analysis（XRD） and density functional theory（DFT） calculations, we suggest that dipeptide P-2 and tripeptide P-3 adopt random coil-like conformations, pentapeptide P-5 and hexapeptide P-6 adopt stable 12-helix conformations in both solution and solid-state. Meanwhile, tetrapeptide P-4 adopt random coil-like conformation in solution and adopt 12-helix conformation in solid state.展开更多
A novel organophosphorus compound containing the structure of bothβ-amino acid andβ-aminophosphonate is designed and synthesized.Arbuzov reaction with P（OEt）_3,the N-Boc protected iodide 3 cannot provide the desir...A novel organophosphorus compound containing the structure of bothβ-amino acid andβ-aminophosphonate is designed and synthesized.Arbuzov reaction with P（OEt）_3,the N-Boc protected iodide 3 cannot provide the desired product but 2-oxazolidinone 4 because of the neighboring-group participation of the Boc moiety.To avoid the intramolecular participation of the carbamates,the Ts protecting group is employed and the Ts-protected iodide 5 affords the target product successfully.展开更多
Sitagliptin is the first new anti-diabetic drug in DPP-Ⅳ inhibitor class. The general synthesis of sitagliptin is by coupling of the β-amino acid fragment with the heterocycle fragment. Though the specific β-amino ...Sitagliptin is the first new anti-diabetic drug in DPP-Ⅳ inhibitor class. The general synthesis of sitagliptin is by coupling of the β-amino acid fragment with the heterocycle fragment. Though the specific β-amino acid can be easily made from the corresponding R-amino acid by Arndt-Eistert hornologation, the optically pure precursor R-amino acid is difficult to prepare. We herein reported a practical protocol to make the trifluorophenyl substituted R-amino acid 4 in 〉99.9% ee and 40.3% yield by the enzymatic resolution employing enantioselective hydrolysis and a general separation procedure. This protocol requires only cheap starting materials and friendly reaction condition. The procedure not only allows people to prepare the drug substance, but also provides an alternative method for prepareing the rare α-amino acid and the subsequent β-amino acid.展开更多
Two new optically active trans-2-atrfinocyclopropanecarboxylic esters （β-ACCs） of optical purity 91%-96% were concisely synthesized via ozonization, oxidation, Curtius rearrangement from commercial available optica...Two new optically active trans-2-atrfinocyclopropanecarboxylic esters （β-ACCs） of optical purity 91%-96% were concisely synthesized via ozonization, oxidation, Curtius rearrangement from commercial available optically active trans-chrysanthemate in total yield 36%.展开更多
文摘The conformations of four β-amino acids in a model peptide environment were investigated using Hartree-Fock (HF) and density functional theory (DFT) methods in gas phase and with solvation. Initial structures were obtained by varying dihedral angles in increments of 45° in the range 0° - 360°. Stable geometries were optimized at both levels of theory with the correlation consistent double-zeta basis set with polarization functions (cc-pVDZ). The results suggest that solvation generally stabilizes the conformations relative to the gas phase and that intramolecular hydrogen bonding may play an important role in the stability of the conformations. The β3 structures, in which the R-group of the amino acid is located on the carbon atom next to the N-terminus, are somewhat more stable relative to each other than the β2 structures which have the R-group on the carbon next to the carbonyl.
基金the National Natural Science Foundation of China（No.21172217）.
文摘A series of novel homochiral β-oligopeptides bearing aryl side chains was designed and synthesized from （S）-β-phenyl-β-amino acid derivatives by solution-phase methods. By means of circular dichroism（CD）, Fourier- transform infrared spectrometry（FTIR）, powder X-ray diffraction analysis（XRD） and density functional theory（DFT） calculations, we suggest that dipeptide P-2 and tripeptide P-3 adopt random coil-like conformations, pentapeptide P-5 and hexapeptide P-6 adopt stable 12-helix conformations in both solution and solid-state. Meanwhile, tetrapeptide P-4 adopt random coil-like conformation in solution and adopt 12-helix conformation in solid state.
文摘A novel organophosphorus compound containing the structure of bothβ-amino acid andβ-aminophosphonate is designed and synthesized.Arbuzov reaction with P（OEt）_3,the N-Boc protected iodide 3 cannot provide the desired product but 2-oxazolidinone 4 because of the neighboring-group participation of the Boc moiety.To avoid the intramolecular participation of the carbamates,the Ts protecting group is employed and the Ts-protected iodide 5 affords the target product successfully.
基金supported in part by grant from Science and Technology Program of Guangdong Province(No. 2007B031503005).
文摘Sitagliptin is the first new anti-diabetic drug in DPP-Ⅳ inhibitor class. The general synthesis of sitagliptin is by coupling of the β-amino acid fragment with the heterocycle fragment. Though the specific β-amino acid can be easily made from the corresponding R-amino acid by Arndt-Eistert hornologation, the optically pure precursor R-amino acid is difficult to prepare. We herein reported a practical protocol to make the trifluorophenyl substituted R-amino acid 4 in 〉99.9% ee and 40.3% yield by the enzymatic resolution employing enantioselective hydrolysis and a general separation procedure. This protocol requires only cheap starting materials and friendly reaction condition. The procedure not only allows people to prepare the drug substance, but also provides an alternative method for prepareing the rare α-amino acid and the subsequent β-amino acid.
基金Finacial support by the National Natural Science Foundation of China(No.2047211)is gratefully acknowledged.
文摘Two new optically active trans-2-atrfinocyclopropanecarboxylic esters （β-ACCs） of optical purity 91%-96% were concisely synthesized via ozonization, oxidation, Curtius rearrangement from commercial available optically active trans-chrysanthemate in total yield 36%.
