An efficient and E-selective monoisomerization of 1-alkenes is developed with a bis(phosphine)-based PCP-type Co complex as the catalyst.The protocol provides an atom-economical approach to trans-2-alkenes with high r...An efficient and E-selective monoisomerization of 1-alkenes is developed with a bis(phosphine)-based PCP-type Co complex as the catalyst.The protocol provides an atom-economical approach to trans-2-alkenes with high regio-and stereoselectivity,featuring mild conditions and wide substrate scope.Mechanistic investigation supports a cobalt-hydride pathway involving reversible alkene insertion/β-H elimination,and the step ofβ-H elimination at the allylic position is likely the rate-determining step.展开更多
Coordination polymerization of renewable β-ocimene has been investigated using asymmetric diiminophosphinate lutetium complex1, β-diketiminate yttrium complex 2, bis(phosphino)carbazolide yttrium complex 3, half-san...Coordination polymerization of renewable β-ocimene has been investigated using asymmetric diiminophosphinate lutetium complex1, β-diketiminate yttrium complex 2, bis(phosphino)carbazolide yttrium complex 3, half-sandwich benzyl fluorenyl scandium complex 4 and pyridyl-methylene-fluorenyl rare-metal complexes 5a–5c. Complexes 1, 4 and 5a–5c show trans-1,2-regioselectivities and high activities, of which 5c exhibits excellent isoselectivity(mmmm>99%). Conversely, complexes 2 and 3 promote β-ocimene polymerization to produce isotactic cis-1,4-polyocimenes(cis-1,4>99%, mm>95%). Diblock copolymers cis-1,4-PIP-block-cis-1,4-POc and cis-1,4-PBD-block-cis-1,4-POc are obtained in one-pot reactions of β-ocimene with isoprene and butadiene using complex 3. Epoxidation and hydroxylation of polyocimene afford functionalized polyolefins with enhanced T_(g)(from-20 ℃ to 79 ℃ and 74 ℃) and hydrophilicity.展开更多
Comprehensive Summary,Herein,we report nickel-catalyzed cross-coupling of gem-difluorinated cyclopropanes with boronic acids,providing the corresponding arylated 2-fluoroallylic scaffolds.This approach used commercial...Comprehensive Summary,Herein,we report nickel-catalyzed cross-coupling of gem-difluorinated cyclopropanes with boronic acids,providing the corresponding arylated 2-fluoroallylic scaffolds.This approach used commercially available phosphine ligand Xantphos to obtain monofluorinated alkenes with high regioselectivity and Z-stereoselectivity.Mechanistic studies proposed a Ni(II)-fluoroallyl pathway and excluded the radical pathway.展开更多
This investigation describes a new precise, sensitive and accurate stereoselective RP-HPLC method for determination of the enantiomers of a novel α- and β-receptor blocking agent, 1-[4-（2-methoxyethyl） phenoxy]-3-...This investigation describes a new precise, sensitive and accurate stereoselective RP-HPLC method for determination of the enantiomers of a novel α- and β-receptor blocking agent, 1-[4-（2-methoxyethyl） phenoxy]-3-[[2-（2- methoxyphenoxy） ethyl]amino]-2-propanol （T J0711）, in rat plasma. GITC was used for precolunm derivatization of T J0711 enantiomers. Enantiomeric resolution was achieved on a Eurospher-100 C18 column （250 mm×4.6 mm ID, 5-μm particle size）, with UV detection at 255 nm, and the mobile phase consisted of acetonitrile and water （58：42, v/v） containing 0.02% glacial acetic acid （v/v）. Using the chromatographic conditions described, T J0711 enantiomers were well resolved with mean retention time of 10.2 and 11.5 min, respectively. Linear response （r〉0.999） was observed over the range of 0.125-12.5 μg/mL of TJ0711 hydrochloride enantiomers. The mean relative standard deviation （RSD%） of the results of within-day precision was ≤ 10%. The proposed method was found to be suitable and accurate for the quantitative determination of T J0711 enantiomers in rat plasma, and it can be used in pharmacokinetic studies.展开更多
A stereoselective and economic synthesis of the carbapenem sidechain (2S, 4S)-4-ace-tylsulphanyl-2-[(S)1-phenylethyl-carbamoyl] pyrrolidine-1-carboxylic acid 4-nitrobenzylester was developed. Due to the effect of spat...A stereoselective and economic synthesis of the carbapenem sidechain (2S, 4S)-4-ace-tylsulphanyl-2-[(S)1-phenylethyl-carbamoyl] pyrrolidine-1-carboxylic acid 4-nitrobenzylester was developed. Due to the effect of spatial hindrance, only the (2S,4S) diastereomer 3 wasobtained by coupling 1 and the inexpensive racemic 2 catalyzed by EEDQ.展开更多
Carbomethoxymethylenetriphenylar 1, or its arsonium bromide in the presence of K2CO3, reacts with 2, 2-dialkyl-1, 3-dioxa-5-substituted-benzal-4, 6-dione 2 to give cis-1-methoxycarbonyl-2-aryl-6, 6-dialky-5, 7-dioxa-s...Carbomethoxymethylenetriphenylar 1, or its arsonium bromide in the presence of K2CO3, reacts with 2, 2-dialkyl-1, 3-dioxa-5-substituted-benzal-4, 6-dione 2 to give cis-1-methoxycarbonyl-2-aryl-6, 6-dialky-5, 7-dioxa-spiro-[2, 5]-4,8-octanadione 3 with a moderate to good yield.展开更多
Substituted PhMgX and PhTi(OCHMe2)4MgX react with 3,5-O-isopropylidene-L-glucurono-γ-lactone 4 to give tetrads 5a-e and its stereoisomers 6a-e Tetrads 5a-e are the important intermediates in the synthesis of howiinol...Substituted PhMgX and PhTi(OCHMe2)4MgX react with 3,5-O-isopropylidene-L-glucurono-γ-lactone 4 to give tetrads 5a-e and its stereoisomers 6a-e Tetrads 5a-e are the important intermediates in the synthesis of howiinol Al and its derivatives. The stereoselectivities of substituted PhTi(OCHMe2)4Mg (5a-e:6a-e ratio, 68-72:32-28) were better than those of substituted PhMgX(33-64:67-36) in the reaction. The effects of different substitUted groups and positions (p-Me, m-Me, o-MeO, p-Cl) of the phenyl ring on their stereoselectivies were not significant.展开更多
Carbomethoxymethylenetriphenylar reacts with ethyl 2-acetyl-3-arylacrylates to afford 2-carbomethoxy-3-aryl-4-carboethoxy-5-methyl-2, 3-dihydrofuran via Michael addition in high to excellent yields with high stereosel...Carbomethoxymethylenetriphenylar reacts with ethyl 2-acetyl-3-arylacrylates to afford 2-carbomethoxy-3-aryl-4-carboethoxy-5-methyl-2, 3-dihydrofuran via Michael addition in high to excellent yields with high stereoselectivity.展开更多
AIM: To study the stereoselectivity of phase Ⅱ glucuronidation metabolism of side-chain propranolol in Chinese Han population. METHODS: Sixteen adult Chinese Han volunteers with an average age of 20 years were given ...AIM: To study the stereoselectivity of phase Ⅱ glucuronidation metabolism of side-chain propranolol in Chinese Han population. METHODS: Sixteen adult Chinese Han volunteers with an average age of 20 years were given a single oral dose of 20 mg racemic propranolol. Human urine at indicated time after administration was collected and S-(-)-propranolol glucuronide and R-(+)-propranolol glucuronide were determined simultaneously by using RP-HPLC. RESULTS: The mean values of k were 0.19±0.04 h-1 and 0.28±0.06 h-1, of t1/2 3.56±0.73 h and 2.45±0.50 h, of Tmax 2.21±0.45 and 1.75±0.33 h, and of Xu0-24 5.65±0.98 and 2.95±0.62 μmoL for S-(-)- and R-(+)-propranolol glucuronide, respectively. The cumulative excretion percentages in urine of closes were 14.7±2.46% and 7.68±1.60% for S-(-)-and R-(+)-propranolol glucuronide, respectively. The results showed the elimination rate constant k of S-(-)-propranolol glucuronide was less than that of R-(+)-propranolol glucuronide; and the elimination half-life (t1/2), Tmax and the cumulative excretion amount (Xu0-24) of R-(+)-propranolol glucuronide were significantly less than that of S-(-)-propranolol glucuronide. CONCLUSION: The propranolol glucuronidation of the side-chain undergoes stereoselective excretion in Chinese Han population after an oral administration of racemic propranolol.展开更多
A potent anxiolytic 4-butyl-α-agarofuran (AF-5) was synthesized from (+)dihydro-carvone. Acid catalyzed hydration of (+)dihydrocarvone and interconversion with β-O-ketone 8 and the key intermediate α,β-unsaturated...A potent anxiolytic 4-butyl-α-agarofuran (AF-5) was synthesized from (+)dihydro-carvone. Acid catalyzed hydration of (+)dihydrocarvone and interconversion with β-O-ketone 8 and the key intermediate α,β-unsaturated ketone 5 made this synthesis more practical.展开更多
Genomic mining has identifi ed a novel microbial alkaline esterase from the Indian Ocean. This esterase was overexpressed in E. coli BL21（DE3） and further functionally characterized. Under optimal conditions（10 mmo...Genomic mining has identifi ed a novel microbial alkaline esterase from the Indian Ocean. This esterase was overexpressed in E. coli BL21（DE3） and further functionally characterized. Under optimal conditions（10 mmol/L substrate, p H 6.0, 2 h at 40 ℃）, this esterase can hydrolyze racemic methyl mandelate to（ R）-methyl mandelate with very high optical purity（e. e. 〉99%） and yield（nearly 90%）. Interestingly, the stereoselectivity of this esterase is opposite to that of two previously reported lipases that can generate（ S）-methyl mandelate through the hydrolysis of racemic methyl mandelate. No organic solvents or other additives were required to optimize the optical purity and production of the fi nal chiral product（R）-methyl mandelate, which can potentially simplify the production procedure of（ R）-methyl mandelate catalyzed by esterase.展开更多
The purpose of this study was to develop and validate a novel and sensitive method for simultaneous enantiomeric analysis of quizalofop-ethyl in tobacco using ultra-performance converge nee chromatography with tandem ...The purpose of this study was to develop and validate a novel and sensitive method for simultaneous enantiomeric analysis of quizalofop-ethyl in tobacco using ultra-performance converge nee chromatography with tandem mass spectrometry(UPC-MS/MS).Sample preparation prior to UPC^2-MS/MS analysis followed a QuEChERS(quick,easy,cheap,effective,rugged and safe)method.The UPC^2-MS/MS method used an Acquity UPC2 Trefoil CEL2 column with a mobile phase of CO2 and methanol.The injection volume was 2 μL and run-time was 6 min with the mobile phase running at 2.0 mL/min flow rate.Column temperature,auto back pressure regulator pressure(ABPR),and modifier solvent were optimized for separation efficiency.Under the optimal conditio ns,the recoveries for all the ena ntiomers were 81.3%-94.8% with relative standard deviations(RSD)less than 5.0% at 0.1,1.0 and 2.0 mg/kg levels,respectively.Good coefficients of determination(R^2≥0.993 7)were achieved for all the studied enantiomers in the tobacco over the concentration range of 10-250 ng/mL.The limits of detection(LODs)varied from 0.02 mg/kg to 0.04 mg/kg,and the limits of quantification(LOQs)were ≤ 0.13 mg/kg.The results confirm that the proposed method is green,convenient and reliable for the enantioselective determination of the enantiomers of quizalofop-ethyl in tobacco.展开更多
The stereoselective synthesis of 2-chloro-4-substituted-phenyl-5,5-dimethyl-1,3,2-dioxaphosphorinan-2-(thi)ones is described. Only single trans-isomers were obtained when 1-substituted-phenyl-2,2-dimethyl-1,3-propaned...The stereoselective synthesis of 2-chloro-4-substituted-phenyl-5,5-dimethyl-1,3,2-dioxaphosphorinan-2-(thi)ones is described. Only single trans-isomers were obtained when 1-substituted-phenyl-2,2-dimethyl-1,3-propanediols (1) reacted with POCl3. But the stereoselectivity of cyclization reaction between (1) and PSCl3 depended greatly upon the reaction condition. The configurational assignments and the ratio of cis-/trans- diastereoisomers of the products were performed on the basis of (HNMR)-H-1, (PNMR)-P-31 and IR spectra and confirmed by X-ray diffraction analyses.展开更多
Objective: To study the stereoselective glucuronidation of carvedilol (CARV) by three Chinese liver microsomes. Methods: The metabolites of CARV were identified by a hydrolysis reaction with β-glucuronidase and HPLC-...Objective: To study the stereoselective glucuronidation of carvedilol (CARV) by three Chinese liver microsomes. Methods: The metabolites of CARV were identified by a hydrolysis reaction with β-glucuronidase and HPLC-MS/MS. The enzyme kinetics for CARV enantiomers glucuronidation was determined by a reversed phase-high pressure liquid chromatogra-phy (RP-HPLC) assay using (S)-propafenone as internal standard after precolumn derivatization with 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosylisothiocyanate. Results: Two CARV glucuronides were found in three Chinese liver microsomes incubated with CARV. The non-linear regression analysis showed that the values of Km and Vmax for (S)-CARV and (R)-CARV enantiomers were (118±44) μmol/L, (2 500±833) pmol/(min·mg protein) and (24±7) μmol/L, (953±399) pmol/(min·mg protein), respectively. Conclusion: These results suggested that there was a significant (P<0.05) stereoselective glucuronidation of CARV enantiomers in three Chinese liver microsomes, which might partly explain the enantioselective pharmacokinetics of CARV.展开更多
A novel and efficient route of synthesizing 1, 2, 4-triazoline-5-ones is reported. The title compounds can be prepared in high yield and purity by the one-pot oxidation and cyclization of 1-acylthiosemicarbazides. The...A novel and efficient route of synthesizing 1, 2, 4-triazoline-5-ones is reported. The title compounds can be prepared in high yield and purity by the one-pot oxidation and cyclization of 1-acylthiosemicarbazides. The reaction is regioselective and stereoselective. The reaction condition is mild.展开更多
Phenylseleno and sulfonyl substituted allyl alcohols were synthesized stereoselectively by the three-component reaction of acetylenic sulfone, phenylselenomagnesium bromide and ketones in one-pot.
（E） -α- （ Methoxyimi no ） -2 - [ 1-（aryloxy） methyl ]-benzeneacetates, the analogues of Kresoxim-methyl, were ste- rcoselectively synthesized with the coupling reaction of 2-methylphenyldiazonium chloride and m...（E） -α- （ Methoxyimi no ） -2 - [ 1-（aryloxy） methyl ]-benzeneacetates, the analogues of Kresoxim-methyl, were ste- rcoselectively synthesized with the coupling reaction of 2-methylphenyldiazonium chloride and methyl 2-hydroxyiminoacetate in the presence of CuSO4/Na2SO3 as a key step, and it was first found that the coupling reaction could give the key intermediate material（ E）- and（Z）-methyl 2-（hydroxyimino）-2-o-tolylacetate with a molar ratio of 14： 1. The （E）-configurations of all these compounds were assigned on the basis of their 2D-NOESY spectra of ^1H NMR. The preliminary bioassays indicate that most of the compounds show an activity against a wide variety of fungi.展开更多
1,4-Dienyl selenides can be stereoselectively synthesized in one pot under mild conditions in good yields by the palladiumcatalyzed hydrostannylation of acetylenic selenides, followed by Stille coupling with allylic b...1,4-Dienyl selenides can be stereoselectively synthesized in one pot under mild conditions in good yields by the palladiumcatalyzed hydrostannylation of acetylenic selenides, followed by Stille coupling with allylic bromides.展开更多
文摘An efficient and E-selective monoisomerization of 1-alkenes is developed with a bis(phosphine)-based PCP-type Co complex as the catalyst.The protocol provides an atom-economical approach to trans-2-alkenes with high regio-and stereoselectivity,featuring mild conditions and wide substrate scope.Mechanistic investigation supports a cobalt-hydride pathway involving reversible alkene insertion/β-H elimination,and the step ofβ-H elimination at the allylic position is likely the rate-determining step.
基金financially supported by the open research fund program of Science and Technology on Aerospace Chemical Power Laboratory (No. STACPL120221B03)the National Natural Science Foundation of China (Nos. s22175059,52073275 and U21A20279)。
文摘Coordination polymerization of renewable β-ocimene has been investigated using asymmetric diiminophosphinate lutetium complex1, β-diketiminate yttrium complex 2, bis(phosphino)carbazolide yttrium complex 3, half-sandwich benzyl fluorenyl scandium complex 4 and pyridyl-methylene-fluorenyl rare-metal complexes 5a–5c. Complexes 1, 4 and 5a–5c show trans-1,2-regioselectivities and high activities, of which 5c exhibits excellent isoselectivity(mmmm>99%). Conversely, complexes 2 and 3 promote β-ocimene polymerization to produce isotactic cis-1,4-polyocimenes(cis-1,4>99%, mm>95%). Diblock copolymers cis-1,4-PIP-block-cis-1,4-POc and cis-1,4-PBD-block-cis-1,4-POc are obtained in one-pot reactions of β-ocimene with isoprene and butadiene using complex 3. Epoxidation and hydroxylation of polyocimene afford functionalized polyolefins with enhanced T_(g)(from-20 ℃ to 79 ℃ and 74 ℃) and hydrophilicity.
基金the funding support of the National Key R&D Program of China(2021YFF0701600)NSFC(21901043,21921003,and 22031004)STCSM(21ZR1445900)and Shanghai Municipal Education Commission(20212308).
文摘Comprehensive Summary,Herein,we report nickel-catalyzed cross-coupling of gem-difluorinated cyclopropanes with boronic acids,providing the corresponding arylated 2-fluoroallylic scaffolds.This approach used commercially available phosphine ligand Xantphos to obtain monofluorinated alkenes with high regioselectivity and Z-stereoselectivity.Mechanistic studies proposed a Ni(II)-fluoroallyl pathway and excluded the radical pathway.
基金supported by a grant from a science andtechnology research program of Hubei provincial government(No.2003AA301B05)the Wuhan New Drug Development Program(No.20066002103)
文摘This investigation describes a new precise, sensitive and accurate stereoselective RP-HPLC method for determination of the enantiomers of a novel α- and β-receptor blocking agent, 1-[4-（2-methoxyethyl） phenoxy]-3-[[2-（2- methoxyphenoxy） ethyl]amino]-2-propanol （T J0711）, in rat plasma. GITC was used for precolunm derivatization of T J0711 enantiomers. Enantiomeric resolution was achieved on a Eurospher-100 C18 column （250 mm×4.6 mm ID, 5-μm particle size）, with UV detection at 255 nm, and the mobile phase consisted of acetonitrile and water （58：42, v/v） containing 0.02% glacial acetic acid （v/v）. Using the chromatographic conditions described, T J0711 enantiomers were well resolved with mean retention time of 10.2 and 11.5 min, respectively. Linear response （r〉0.999） was observed over the range of 0.125-12.5 μg/mL of TJ0711 hydrochloride enantiomers. The mean relative standard deviation （RSD%） of the results of within-day precision was ≤ 10%. The proposed method was found to be suitable and accurate for the quantitative determination of T J0711 enantiomers in rat plasma, and it can be used in pharmacokinetic studies.
文摘A stereoselective and economic synthesis of the carbapenem sidechain (2S, 4S)-4-ace-tylsulphanyl-2-[(S)1-phenylethyl-carbamoyl] pyrrolidine-1-carboxylic acid 4-nitrobenzylester was developed. Due to the effect of spatial hindrance, only the (2S,4S) diastereomer 3 wasobtained by coupling 1 and the inexpensive racemic 2 catalyzed by EEDQ.
文摘Carbomethoxymethylenetriphenylar 1, or its arsonium bromide in the presence of K2CO3, reacts with 2, 2-dialkyl-1, 3-dioxa-5-substituted-benzal-4, 6-dione 2 to give cis-1-methoxycarbonyl-2-aryl-6, 6-dialky-5, 7-dioxa-spiro-[2, 5]-4,8-octanadione 3 with a moderate to good yield.
文摘Substituted PhMgX and PhTi(OCHMe2)4MgX react with 3,5-O-isopropylidene-L-glucurono-γ-lactone 4 to give tetrads 5a-e and its stereoisomers 6a-e Tetrads 5a-e are the important intermediates in the synthesis of howiinol Al and its derivatives. The stereoselectivities of substituted PhTi(OCHMe2)4Mg (5a-e:6a-e ratio, 68-72:32-28) were better than those of substituted PhMgX(33-64:67-36) in the reaction. The effects of different substitUted groups and positions (p-Me, m-Me, o-MeO, p-Cl) of the phenyl ring on their stereoselectivies were not significant.
文摘Carbomethoxymethylenetriphenylar reacts with ethyl 2-acetyl-3-arylacrylates to afford 2-carbomethoxy-3-aryl-4-carboethoxy-5-methyl-2, 3-dihydrofuran via Michael addition in high to excellent yields with high stereoselectivity.
基金Supported by the National Natural Science Foundation of China, No. 30225047
文摘AIM: To study the stereoselectivity of phase Ⅱ glucuronidation metabolism of side-chain propranolol in Chinese Han population. METHODS: Sixteen adult Chinese Han volunteers with an average age of 20 years were given a single oral dose of 20 mg racemic propranolol. Human urine at indicated time after administration was collected and S-(-)-propranolol glucuronide and R-(+)-propranolol glucuronide were determined simultaneously by using RP-HPLC. RESULTS: The mean values of k were 0.19±0.04 h-1 and 0.28±0.06 h-1, of t1/2 3.56±0.73 h and 2.45±0.50 h, of Tmax 2.21±0.45 and 1.75±0.33 h, and of Xu0-24 5.65±0.98 and 2.95±0.62 μmoL for S-(-)- and R-(+)-propranolol glucuronide, respectively. The cumulative excretion percentages in urine of closes were 14.7±2.46% and 7.68±1.60% for S-(-)-and R-(+)-propranolol glucuronide, respectively. The results showed the elimination rate constant k of S-(-)-propranolol glucuronide was less than that of R-(+)-propranolol glucuronide; and the elimination half-life (t1/2), Tmax and the cumulative excretion amount (Xu0-24) of R-(+)-propranolol glucuronide were significantly less than that of S-(-)-propranolol glucuronide. CONCLUSION: The propranolol glucuronidation of the side-chain undergoes stereoselective excretion in Chinese Han population after an oral administration of racemic propranolol.
文摘A potent anxiolytic 4-butyl-α-agarofuran (AF-5) was synthesized from (+)dihydro-carvone. Acid catalyzed hydration of (+)dihydrocarvone and interconversion with β-O-ketone 8 and the key intermediate α,β-unsaturated ketone 5 made this synthesis more practical.
基金Supported by the National Natural Science Foundation of China(No.21302199)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA11030404)+1 种基金the Project of“Engineering HighPerformance Microorganisms for Advanced Bio-Based Manufacturing”from the Chinese Academy of Sciences(No.KGZD-EW-606)the Guangzhou Science and Technology Plan Projects(No.201510010012)
文摘Genomic mining has identifi ed a novel microbial alkaline esterase from the Indian Ocean. This esterase was overexpressed in E. coli BL21（DE3） and further functionally characterized. Under optimal conditions（10 mmol/L substrate, p H 6.0, 2 h at 40 ℃）, this esterase can hydrolyze racemic methyl mandelate to（ R）-methyl mandelate with very high optical purity（e. e. 〉99%） and yield（nearly 90%）. Interestingly, the stereoselectivity of this esterase is opposite to that of two previously reported lipases that can generate（ S）-methyl mandelate through the hydrolysis of racemic methyl mandelate. No organic solvents or other additives were required to optimize the optical purity and production of the fi nal chiral product（R）-methyl mandelate, which can potentially simplify the production procedure of（ R）-methyl mandelate catalyzed by esterase.
文摘The purpose of this study was to develop and validate a novel and sensitive method for simultaneous enantiomeric analysis of quizalofop-ethyl in tobacco using ultra-performance converge nee chromatography with tandem mass spectrometry(UPC-MS/MS).Sample preparation prior to UPC^2-MS/MS analysis followed a QuEChERS(quick,easy,cheap,effective,rugged and safe)method.The UPC^2-MS/MS method used an Acquity UPC2 Trefoil CEL2 column with a mobile phase of CO2 and methanol.The injection volume was 2 μL and run-time was 6 min with the mobile phase running at 2.0 mL/min flow rate.Column temperature,auto back pressure regulator pressure(ABPR),and modifier solvent were optimized for separation efficiency.Under the optimal conditio ns,the recoveries for all the ena ntiomers were 81.3%-94.8% with relative standard deviations(RSD)less than 5.0% at 0.1,1.0 and 2.0 mg/kg levels,respectively.Good coefficients of determination(R^2≥0.993 7)were achieved for all the studied enantiomers in the tobacco over the concentration range of 10-250 ng/mL.The limits of detection(LODs)varied from 0.02 mg/kg to 0.04 mg/kg,and the limits of quantification(LOQs)were ≤ 0.13 mg/kg.The results confirm that the proposed method is green,convenient and reliable for the enantioselective determination of the enantiomers of quizalofop-ethyl in tobacco.
文摘The stereoselective synthesis of 2-chloro-4-substituted-phenyl-5,5-dimethyl-1,3,2-dioxaphosphorinan-2-(thi)ones is described. Only single trans-isomers were obtained when 1-substituted-phenyl-2,2-dimethyl-1,3-propanediols (1) reacted with POCl3. But the stereoselectivity of cyclization reaction between (1) and PSCl3 depended greatly upon the reaction condition. The configurational assignments and the ratio of cis-/trans- diastereoisomers of the products were performed on the basis of (HNMR)-H-1, (PNMR)-P-31 and IR spectra and confirmed by X-ray diffraction analyses.
基金the National Natural Science Foundation of China (No. 30225047)the Science and Technology Foundation of Zhejiang Province, China (No. 2005C13026)
文摘Objective: To study the stereoselective glucuronidation of carvedilol (CARV) by three Chinese liver microsomes. Methods: The metabolites of CARV were identified by a hydrolysis reaction with β-glucuronidase and HPLC-MS/MS. The enzyme kinetics for CARV enantiomers glucuronidation was determined by a reversed phase-high pressure liquid chromatogra-phy (RP-HPLC) assay using (S)-propafenone as internal standard after precolumn derivatization with 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosylisothiocyanate. Results: Two CARV glucuronides were found in three Chinese liver microsomes incubated with CARV. The non-linear regression analysis showed that the values of Km and Vmax for (S)-CARV and (R)-CARV enantiomers were (118±44) μmol/L, (2 500±833) pmol/(min·mg protein) and (24±7) μmol/L, (953±399) pmol/(min·mg protein), respectively. Conclusion: These results suggested that there was a significant (P<0.05) stereoselective glucuronidation of CARV enantiomers in three Chinese liver microsomes, which might partly explain the enantioselective pharmacokinetics of CARV.
基金the NNSFC(No.20172027)the Natural Science Foundation of Tianjin(05YFJMJC00600)for financial support.
文摘A novel and efficient route of synthesizing 1, 2, 4-triazoline-5-ones is reported. The title compounds can be prepared in high yield and purity by the one-pot oxidation and cyclization of 1-acylthiosemicarbazides. The reaction is regioselective and stereoselective. The reaction condition is mild.
基金supported by the National Natural Science Foundation of China(No.29772007)
文摘Phenylseleno and sulfonyl substituted allyl alcohols were synthesized stereoselectively by the three-component reaction of acetylenic sulfone, phenylselenomagnesium bromide and ketones in one-pot.
文摘（E） -α- （ Methoxyimi no ） -2 - [ 1-（aryloxy） methyl ]-benzeneacetates, the analogues of Kresoxim-methyl, were ste- rcoselectively synthesized with the coupling reaction of 2-methylphenyldiazonium chloride and methyl 2-hydroxyiminoacetate in the presence of CuSO4/Na2SO3 as a key step, and it was first found that the coupling reaction could give the key intermediate material（ E）- and（Z）-methyl 2-（hydroxyimino）-2-o-tolylacetate with a molar ratio of 14： 1. The （E）-configurations of all these compounds were assigned on the basis of their 2D-NOESY spectra of ^1H NMR. The preliminary bioassays indicate that most of the compounds show an activity against a wide variety of fungi.
基金the National Natural Science Foundation of China (No.20462002)Natural Science Foundation of Jiangxi Province (No.2007GZW0172) for financial support.
文摘1,4-Dienyl selenides can be stereoselectively synthesized in one pot under mild conditions in good yields by the palladiumcatalyzed hydrostannylation of acetylenic selenides, followed by Stille coupling with allylic bromides.
