A practical synthesis of （S）-N-（2-ethyl-6-methylphenyl）alanine, a key intermediate for （S）-metolachlor, was completed by means of lipase-catalyzed hydrolytic kinetic resolution and chemical racemization of the r...A practical synthesis of （S）-N-（2-ethyl-6-methylphenyl）alanine, a key intermediate for （S）-metolachlor, was completed by means of lipase-catalyzed hydrolytic kinetic resolution and chemical racemization of the remaining ester. The effects of operating temperature and enzyme concentration on the activity and enantioselectivity of enzyme were initially studied, and it was found that the enantioselectivity of CAL-B towards the resolution was not high enough to obtain enantiomerically pure compound（E=12.1）. When diethyl ether（15%, volume fraction） was added in the reaction medium, the lipase gave an excellent enantioselectivity（E=117.8）, which is about 9.7-fold that in pure buffered aqueous solution. For overcoming the limitation of a maximum theoretical yield of 50%, the acid product was separated from the remaining ester by a simple extraction procedure and the remaining ester was racemized with aldehyde and acetic acid under microwave irradiation or conventional heating condition, The results show the microwave irradiation was more effective than the conventional heating method and gave the desired （R,S）-N-（2- ethyl-6-methylphenyl）alanine methyl ester a high yield（92%） with R/S=50/50 in 1 h.展开更多
The crystal and molecular structure of copper(Ⅱ) dimeric complex of S-methyl-B-N-(pyridine N-oxide-2-ylmethylidene) dithiocarbazate with acetonitrile, [CuL (CH3CN)]2 (ClO4)2, was determined by X-ray diffraction. The ...The crystal and molecular structure of copper(Ⅱ) dimeric complex of S-methyl-B-N-(pyridine N-oxide-2-ylmethylidene) dithiocarbazate with acetonitrile, [CuL (CH3CN)]2 (ClO4)2, was determined by X-ray diffraction. The complex crystalizes in monoclinic system with space group P21/n, a= 7. 685(2), 6=20.160(6), c= 10. 847(5) A ,B = 107.89(3), Z=2,Dc=1.788 g/cm3, F(000) = 835. 8, u= 18. 17 cm-1(Moka,R= 0. 057.Each Cu(Ⅱ) ion in the complex is surrounded by a distorted square pyramidal. The basal plane is comprised of S, N and O atoms of one ligand together with a N atom of the solvent--acetonitrile, while the axial position is occupied by the S atom of the other ligand. The bond length of Cu-S(bridging) is 3. 038A . and Cu-Cu distance is 3. 700A.展开更多
以(S)-脯氨酸1为原料,在酸性条件和金属锌的催化还原作用下,通过与甲醛反应,高收率获得了(S)-N-甲基脯氨酸2。然后在N,N-二甲基乙酰胺(DMAc)和CH_2Cl_2体系中,(S)-N-甲基脯氨酸2与SOCl_2在0℃下反应20min,制得的酰氯不经提纯直接与加入...以(S)-脯氨酸1为原料,在酸性条件和金属锌的催化还原作用下,通过与甲醛反应,高收率获得了(S)-N-甲基脯氨酸2。然后在N,N-二甲基乙酰胺(DMAc)和CH_2Cl_2体系中,(S)-N-甲基脯氨酸2与SOCl_2在0℃下反应20min,制得的酰氯不经提纯直接与加入的甲醇在25℃下反应5h,获得中间产物(S)-N-甲基脯氨酸甲酯3。最后以LiAlH_4为还原剂,四氢呋喃为溶剂,高收率(87.3%)地获得了(S)-N-甲基脯氨醇4。产物结构经~1 H NMR、^(13)C NMR、HRMS确证。展开更多
基金Supported by the National Natural Science Foundation of China(No.20802025)the Hi-Tech Research and Development Program of China(No.2007AA021306)Jilin Provincial Science & Technology Sustentation Program,China(No.20070553)
文摘A practical synthesis of （S）-N-（2-ethyl-6-methylphenyl）alanine, a key intermediate for （S）-metolachlor, was completed by means of lipase-catalyzed hydrolytic kinetic resolution and chemical racemization of the remaining ester. The effects of operating temperature and enzyme concentration on the activity and enantioselectivity of enzyme were initially studied, and it was found that the enantioselectivity of CAL-B towards the resolution was not high enough to obtain enantiomerically pure compound（E=12.1）. When diethyl ether（15%, volume fraction） was added in the reaction medium, the lipase gave an excellent enantioselectivity（E=117.8）, which is about 9.7-fold that in pure buffered aqueous solution. For overcoming the limitation of a maximum theoretical yield of 50%, the acid product was separated from the remaining ester by a simple extraction procedure and the remaining ester was racemized with aldehyde and acetic acid under microwave irradiation or conventional heating condition, The results show the microwave irradiation was more effective than the conventional heating method and gave the desired （R,S）-N-（2- ethyl-6-methylphenyl）alanine methyl ester a high yield（92%） with R/S=50/50 in 1 h.
文摘The crystal and molecular structure of copper(Ⅱ) dimeric complex of S-methyl-B-N-(pyridine N-oxide-2-ylmethylidene) dithiocarbazate with acetonitrile, [CuL (CH3CN)]2 (ClO4)2, was determined by X-ray diffraction. The complex crystalizes in monoclinic system with space group P21/n, a= 7. 685(2), 6=20.160(6), c= 10. 847(5) A ,B = 107.89(3), Z=2,Dc=1.788 g/cm3, F(000) = 835. 8, u= 18. 17 cm-1(Moka,R= 0. 057.Each Cu(Ⅱ) ion in the complex is surrounded by a distorted square pyramidal. The basal plane is comprised of S, N and O atoms of one ligand together with a N atom of the solvent--acetonitrile, while the axial position is occupied by the S atom of the other ligand. The bond length of Cu-S(bridging) is 3. 038A . and Cu-Cu distance is 3. 700A.
文摘以(S)-脯氨酸1为原料,在酸性条件和金属锌的催化还原作用下,通过与甲醛反应,高收率获得了(S)-N-甲基脯氨酸2。然后在N,N-二甲基乙酰胺(DMAc)和CH_2Cl_2体系中,(S)-N-甲基脯氨酸2与SOCl_2在0℃下反应20min,制得的酰氯不经提纯直接与加入的甲醇在25℃下反应5h,获得中间产物(S)-N-甲基脯氨酸甲酯3。最后以LiAlH_4为还原剂,四氢呋喃为溶剂,高收率(87.3%)地获得了(S)-N-甲基脯氨醇4。产物结构经~1 H NMR、^(13)C NMR、HRMS确证。
