The authors regret that in the original article,the structure of(–)-swainsonine(1)in Graphical abstract,Fig.1,Schemes 1 and 3 was incorrect.The correct structure is shown here.
3-Deoxy-D-manno–oct-2-ulosonic acid(Kdo)is widely distributed in bacteria,and the synthesis of Kdocontaining oligosaccharides is important for the development of novel antibiotics and immunological agents.We have rec...3-Deoxy-D-manno–oct-2-ulosonic acid(Kdo)is widely distributed in bacteria,and the synthesis of Kdocontaining oligosaccharides is important for the development of novel antibiotics and immunological agents.We have recently developed a strategy to achieveα-stereocontrolled glycosylation using a C3-p-tolylthio-substituted Kdo phosphite donor.The wide substrate scope and high reactivity of the donors enabled the efficient synthesis of a series of Kdo-containing glycosides with completeα-stereoselectivity and without the formation of 2,3-ene byproducts.In this study,we improved the method by replacing the leaving group diethyl phosphite with fluoride,which enhanced the stability of the donor and led to cleaner reaction.Furthermore,the substrate range was expanded by synthesizing a series of Kdo O/C/S/Nglycosides,which also opened up a new avenue for the synthesis of CMP-Kdo synthase inhibitors.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
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 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
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
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
A short formal stereoselective synthesis of （-）-swainsonine （1） is described. Our synthesis started with the versatile building block （R）-3-benzyloxyglutarimide 5. Through controlled regioselective reduction, Le...A short formal stereoselective synthesis of （-）-swainsonine （1） is described. Our synthesis started with the versatile building block （R）-3-benzyloxyglutarimide 5. Through controlled regioselective reduction, Ley＇s-sulfone chemistry （N-α-sulfonylation and ZnCl2-catalyzed N-α-amidovinylation）, an RCM reaction, and an amide reduction, the synthesis of unsaturated indolizidine （8R,8aS）-3 has been achieved in five steps. The indolizidine （8R,8aS）-3 is an advanced intermediate toward the synthesis of （-）-swainsonine （1）.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
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
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
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
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
A family of the 3,6-branched Fuziα-glucans including the pentasaccharide repeating unit as well as its di-and trimers were efficiently achieved via a one-pot and convergent glycosylation strategy.All the protectedα-...A family of the 3,6-branched Fuziα-glucans including the pentasaccharide repeating unit as well as its di-and trimers were efficiently achieved via a one-pot and convergent glycosylation strategy.All the protectedα-glucans up to 15-mer were assembled with high yields and excellentα-stereoselectivity,which was secured by the synergisticα-directing effects of the Tol SCl/Ag OTf promotion system and the stericβ-facial shielding of bulky saccharide residues linked at the 6-O-position of glucosyl donors.Moreover,the 3,6-branched architecture of glycosyl donor was revealed to be more favorable for theα-selective glucosidation of primary hydroxyl group,especially in the case of large oligosaccharide acceptor.The structurally well-defined syntheticα-glucans would be useful for various biological studies.展开更多
A simple and convenient procedure for stercoselective synthesis of （Z）-allyl selenides has been developed by a one-pot reaction of diselenides with Baylis-Hillman adducts in the presence of samarium metal-trimethyls...A simple and convenient procedure for stercoselective synthesis of （Z）-allyl selenides has been developed by a one-pot reaction of diselenides with Baylis-Hillman adducts in the presence of samarium metal-trimethylsilyl chloride under mild conditions. Presumably, the diselenides are cleaved by Sm/TMSCI system to form selemde anions, which then undergo SN2＇ substitution of Baylis-Hillman adducts to produce the （Z）-allyl selenides.展开更多
Carbon-carbon double bond functional groups are often protected through a popular bromination/debromination method because of their reactivity. An ultrasonic-enhanced stereoselective debromination of vic-dibromides wi...Carbon-carbon double bond functional groups are often protected through a popular bromination/debromination method because of their reactivity. An ultrasonic-enhanced stereoselective debromination of vic-dibromides with metallic zinc powder in aqueous media has been developed, which generates E-alkenes with excellent yields. The reactivity of vic-dibromides decreases in the order of 1,2-dibromo-1,2-diphenylethane>1,2-dibromo-1-phenylethane>1,2-dibromo-1,2-dialkylethane.展开更多
1-(4-hydroxy-3-methoxyphenyl)-2-(4-formyl-2-methoxyphenoxy)-propane-1,3-diol. A 8-O-4' neolignan, has been stereoselectively synthesized in eight steps from ferulic acid, and the directly cis opening of epoxide in...1-(4-hydroxy-3-methoxyphenyl)-2-(4-formyl-2-methoxyphenoxy)-propane-1,3-diol. A 8-O-4' neolignan, has been stereoselectively synthesized in eight steps from ferulic acid, and the directly cis opening of epoxide in eposidation and Mitsunobu reaction were used ingeniously as two key steps with high stereoselectively.展开更多
A precursor of sarcophytol-Q, (11 S) -3, 7, 11, 15-tetramethyl-11-hydroxy-14-oxo-3E, 7E, 12E-hexadecatrienal, was synthesized by a convergent and stereoselective manner from geraniol via nine steps employing asymmetri...A precursor of sarcophytol-Q, (11 S) -3, 7, 11, 15-tetramethyl-11-hydroxy-14-oxo-3E, 7E, 12E-hexadecatrienal, was synthesized by a convergent and stereoselective manner from geraniol via nine steps employing asymmetric Sharpless epoxidation and be (n-BuLi)-induce dehydrohalogenation rearrangement of chiral epoxy chloride (4) and the phase transfer catalytic coupling reaction of allylic phenyl sulfone (9) with chiral allylic chloride (6) as key steps.展开更多
The tacticity of vinyl polymers is a key factor affecting the properties of materials.Recently,organic Brønsted acids have been demonstrated as effective catalysts for the development of highly stereoselective ca...The tacticity of vinyl polymers is a key factor affecting the properties of materials.Recently,organic Brønsted acids have been demonstrated as effective catalysts for the development of highly stereoselective cationic reversible addition-fragmentation chain transfer(RAFT)polymerizations of vinyl ethers,in which the use of RAFT agents could allow the control the molecular weight and tacticity of polymer products simultaneously.However,the effect of RAFT agents on the tacticity-regulation remains elusive and lacks of investigation.In this study,we synthesized four types of RAFT agents and evaluated their influence in the stereoselective cationic polymerization of isobutyl vinyl ether in the presence of PADI as a Brønsted acid catalyst,which unveils that the Z group of RAFT agents could not only affect the polydispersity of the products,but also exert a profound effect on the stereoselectivity.After extensive screening of the RAFT agents,high stereoregularity(isotacticity,90%m)was obtained when using dithiocarbonate ester-type RAFT agents with a benzyloxy Z group.展开更多
文摘The authors regret that in the original article,the structure of(–)-swainsonine(1)in Graphical abstract,Fig.1,Schemes 1 and 3 was incorrect.The correct structure is shown here.
基金supported by the National Key R&D Program of China(Nos.2022YFF1203005,2022YFC2303700)supported by the National Natural Science Foundation of China(Nos.81930097,82151223).
文摘3-Deoxy-D-manno–oct-2-ulosonic acid(Kdo)is widely distributed in bacteria,and the synthesis of Kdocontaining oligosaccharides is important for the development of novel antibiotics and immunological agents.We have recently developed a strategy to achieveα-stereocontrolled glycosylation using a C3-p-tolylthio-substituted Kdo phosphite donor.The wide substrate scope and high reactivity of the donors enabled the efficient synthesis of a series of Kdo-containing glycosides with completeα-stereoselectivity and without the formation of 2,3-ene byproducts.In this study,we improved the method by replacing the leaving group diethyl phosphite with fluoride,which enhanced the stability of the donor and led to cleaner reaction.Furthermore,the substrate range was expanded by synthesizing a series of Kdo O/C/S/Nglycosides,which also opened up a new avenue for the synthesis of CMP-Kdo synthase inhibitors.
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 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.
基金financial support from the National Basic Research Program(973 Program)of China(No. 2010CB833200)the NSF of China(Nos.21332007,21072160)the Program for Changjiang Scholars and Innovative Research Team in University(PCSIRT)of Ministry of Education,China for financial support
文摘A short formal stereoselective synthesis of （-）-swainsonine （1） is described. Our synthesis started with the versatile building block （R）-3-benzyloxyglutarimide 5. Through controlled regioselective reduction, Ley＇s-sulfone chemistry （N-α-sulfonylation and ZnCl2-catalyzed N-α-amidovinylation）, an RCM reaction, and an amide reduction, the synthesis of unsaturated indolizidine （8R,8aS）-3 has been achieved in five steps. The indolizidine （8R,8aS）-3 is an advanced intermediate toward the synthesis of （-）-swainsonine （1）.
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.
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.
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.
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.22177060)the Young Scholars Program of Shandong University(No.2018WLJH41)+1 种基金the Open Projects Fund of Shandong Key Laboratory of Carbohydrate Chemistry and Glycobiology,Shandong University(No.2021CCG06)the Central Government Guide Local Science and Technology Development Funds(No.YDZX20203700002579)。
文摘A family of the 3,6-branched Fuziα-glucans including the pentasaccharide repeating unit as well as its di-and trimers were efficiently achieved via a one-pot and convergent glycosylation strategy.All the protectedα-glucans up to 15-mer were assembled with high yields and excellentα-stereoselectivity,which was secured by the synergisticα-directing effects of the Tol SCl/Ag OTf promotion system and the stericβ-facial shielding of bulky saccharide residues linked at the 6-O-position of glucosyl donors.Moreover,the 3,6-branched architecture of glycosyl donor was revealed to be more favorable for theα-selective glucosidation of primary hydroxyl group,especially in the case of large oligosaccharide acceptor.The structurally well-defined syntheticα-glucans would be useful for various biological studies.
基金Project (No. 2004C21032) supported by the Key Technologies R &D Program of Zhejiang Province, China
文摘A simple and convenient procedure for stercoselective synthesis of （Z）-allyl selenides has been developed by a one-pot reaction of diselenides with Baylis-Hillman adducts in the presence of samarium metal-trimethylsilyl chloride under mild conditions. Presumably, the diselenides are cleaved by Sm/TMSCI system to form selemde anions, which then undergo SN2＇ substitution of Baylis-Hillman adducts to produce the （Z）-allyl selenides.
基金Supported by the National Natural Science Foundation of China(No.2 0 372 0 2 4 2 0 172 0 18) +2 种基金the Excellent ScientistFoundation of Anhui ProvinceChina(No.2 0 0 10 4 0 ) the Natural Science Foundation of the Educational Departm entof AnhuiProvince
文摘Carbon-carbon double bond functional groups are often protected through a popular bromination/debromination method because of their reactivity. An ultrasonic-enhanced stereoselective debromination of vic-dibromides with metallic zinc powder in aqueous media has been developed, which generates E-alkenes with excellent yields. The reactivity of vic-dibromides decreases in the order of 1,2-dibromo-1,2-diphenylethane>1,2-dibromo-1-phenylethane>1,2-dibromo-1,2-dialkylethane.
基金the National Natural Science Foundation of China (No.29972015).
文摘1-(4-hydroxy-3-methoxyphenyl)-2-(4-formyl-2-methoxyphenoxy)-propane-1,3-diol. A 8-O-4' neolignan, has been stereoselectively synthesized in eight steps from ferulic acid, and the directly cis opening of epoxide in eposidation and Mitsunobu reaction were used ingeniously as two key steps with high stereoselectively.
文摘A precursor of sarcophytol-Q, (11 S) -3, 7, 11, 15-tetramethyl-11-hydroxy-14-oxo-3E, 7E, 12E-hexadecatrienal, was synthesized by a convergent and stereoselective manner from geraniol via nine steps employing asymmetric Sharpless epoxidation and be (n-BuLi)-induce dehydrohalogenation rearrangement of chiral epoxy chloride (4) and the phase transfer catalytic coupling reaction of allylic phenyl sulfone (9) with chiral allylic chloride (6) as key steps.
基金supported by the Recruitment Program of Global Experts of China,the National Natural Science Foundation of China(Nos.21602028 and 22371240)Beijing National Laboratory for Molecular Sciences(No.BNLMS201913)100-Talent program of Fujian,Fuzhou University and Xiamen University.
文摘The tacticity of vinyl polymers is a key factor affecting the properties of materials.Recently,organic Brønsted acids have been demonstrated as effective catalysts for the development of highly stereoselective cationic reversible addition-fragmentation chain transfer(RAFT)polymerizations of vinyl ethers,in which the use of RAFT agents could allow the control the molecular weight and tacticity of polymer products simultaneously.However,the effect of RAFT agents on the tacticity-regulation remains elusive and lacks of investigation.In this study,we synthesized four types of RAFT agents and evaluated their influence in the stereoselective cationic polymerization of isobutyl vinyl ether in the presence of PADI as a Brønsted acid catalyst,which unveils that the Z group of RAFT agents could not only affect the polydispersity of the products,but also exert a profound effect on the stereoselectivity.After extensive screening of the RAFT agents,high stereoregularity(isotacticity,90%m)was obtained when using dithiocarbonate ester-type RAFT agents with a benzyloxy Z group.
