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Amir H. Hoveyda - One of the best experts on this subject based on the ideXlab platform.
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an efficient practical and Enantioselective Method for synthesis of homoallenylamides catalyzed by an aminoalcohol derived boron based catalyst
2014Co-Authors: Hao Wu, Fredrik Haeffner, Amir H. HoveydaAbstract:The first general Enantioselective allenyl addition to a range of aromatic and aliphatic aldehyde derived imines is presented.
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an efficient practical and Enantioselective Method for synthesis of homoallenylamides catalyzed by an aminoalcohol derived boron based catalyst
2014Co-Authors: Hao Wu, Fredrik Haeffner, Amir H. HoveydaAbstract:A practical catalytic Method for Enantioselective addition of an allene unit to aldimines is disclosed. Transformations are promoted by an in-situ-generated B-based catalyst that is derived from a simple, robust, and readily accessible (in multigram quantities) chiral aminoalcohol. A range of aryl-, heteroaryl-, and alkyl-substituted homoallenylamides can be obtained in 66–91% yield and 84:16 to >99:1 enantiomeric ratio through reactions performed at ambient temperature and in the presence of 0.1–3.0 mol% of the chiral catalyst and a commercially available allenylboron reagent. The catalytic protocol does not require strict anhydrous conditions, can be performed on gram scale, and promotes highly selective addition of an allenyl unit (vs a propargyl group). The utility of the approach is demonstrated through development of succinct approaches to syntheses of anisomycin and epi-cytoxazone.
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combining nhc cu and bronsted base catalysis Enantioselective allylic substitution conjugate additions with alkynylaluminum reagents and stereospecific isomerization of the products to trisubstituted allenes
2013Co-Authors: Jennifer A Dabrowski, Fredrik Haeffner, Amir H. HoveydaAbstract:Among different types of unsaturated carbon-carbon bonds, allenes carry significant but relatively unexplored potential in chemical synthesis.[1] Research in more recent years has been focused on development of catalytic Enantioselective protocols that generate allenes[1] or on providing access to molecules that contain them.[2] Various procedures have been introduced for site-, chemo- and/or stereoselective allene functionalization.[3] Nonetheless, Methods of preparation have been largely centered on disubstituted variants;[1] protocols that furnish the trisubstituted allenes, especially those that are catalytic, are less common and typically involve nucleophilic SN2′ additions to enantiomerically enriched alkynyl entities.[4] Among alternative approaches, strategies that deliver trisubstituted allenes through catalytic isomerization of alkyne-containing substrates[5] pose an attractive but somewhat uncharted pathway.[6] We thus envisioned the plan outlined in Scheme 1, involving the feasibility of catalytic and stereospecific isomerization of an enantiomerically enriched alkyne.[7] Bringing such a goal to fruition, however, required a stereoselective catalytic process to effect the desired 1,3-proton shift as well as an efficient, site- and Enantioselective Method for synthesis of the requisite substrates. Indeed, catalytic Enantioselective allylic substitution (EAS) reactions[8] with alkynyl nucleophiles are rare;[9] related catalytic Enantioselective processes that generate tertiary stereogenic carbon centers are unknown.[10] Herein, we describe the realization of the plan illustrated in Scheme 1 to address the abovementioned shortcomings.
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a robust efficient and highly Enantioselective Method for synthesis of homopropargyl amines
2012Co-Authors: Erika M Vieira, Fredrik Haeffner, Marc L Snapper, Amir H. HoveydaAbstract:The first general, practical, scalable, and efficient Method for the synthesis of the title compounds is developed by using an inexpensive metal salt and a readily preparable ligand (five steps).
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a robust efficient and highly Enantioselective Method for synthesis of homopropargyl amines
2012Co-Authors: Erika M Vieira, Fredrik Haeffner, Marc L Snapper, Amir H. HoveydaAbstract:Catalytic protocols that generate a-branched amines efficiently and Enantioselectively facilitate the preparation of many important biologically active molecules.[1]Among such entities are homopropargyl amines, used in the total synthesis of a number of natural products.[2] Several investigations have adopted the chiral auxiliary strategy; the desired products are obtained in high diastereoselectivity as trimethylsilyl-substituted alkynes.[3] In contrast, the corresponding catalytic protocols are scarce. The first relevant report included three examples of reactions of allenyl stannanes with a glyoxylate-derived tosylimine,[4] affording homopropargyl sulfonamides in 34–96% yield and 55:45–93:7 enantiomeric ratio (e.r.).[5] A notable recent advance entails Enantioselective additions of a readily available allenylboron to tosylimines catalyzed by a Ag-phosphine catalyst to furnish a wider range of products and higher enantioselectivity (87:13 to more than 98:2 e.r.). Nonetheless, reactions of substrates that do not bear an aryl substituent proved to be less efficient, those of enolizable alkyl-substituted tosylimines were not reported and, as with the aforementioned initial development, removal of the tosyl unit requires strong reducing conditions.[6-8]
Wenwei Lin - One of the best experts on this subject based on the ideXlab platform.
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expanding the scope of primary amine catalysis stereoselective synthesis of indanedione fused 2 6 disubstituted trans spirocyclohexanones
2016Co-Authors: Madhusudhan G Reddy, Kai Hong Hsieh, Chia Jui Lee, Utpal Das, Wenwei LinAbstract:A cinchona-alkaloid-derived chiral primary-amine-catalyzed Enantioselective Method for the synthesis of the thermodynamically less stable indanedione-fused 2,6-trans-disubstituted spirocyclohexanones is demonstrated. Both the enantiomeric forms of the trans isomer are obtained in excellent yields and enantioselectivities. Furthermore, one of the enantiopure trans-spiranes bearing an additional α-substitution on the cyclohexanone ring was then epimerized into its thermodynamically stable cis counterpart, with little loss of enantioselectivity to demonstrate the feasibility of such a transformation. Mechanistic investigations revealed two competing pathways, a concerted Diels–Alder reaction and a stepwise Michael addition, for the formation of corresponding products.
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Expanding the Scope of Primary Amine Catalysis: Stereoselective Synthesis of Indanedione-Fused 2,6-Disubstituted trans-Spirocyclohexanones
2016Co-Authors: Madhusudhan G Reddy, Kai Hong Hsieh, Chia Jui Lee, Utpal Das, Wenwei LinAbstract:A cinchona-alkaloid-derived chiral primary-amine-catalyzed Enantioselective Method for the synthesis of the thermodynamically less stable indanedione-fused 2,6-trans-disubstituted spirocyclohexanones is demonstrated. Both the enantiomeric forms of the trans isomer are obtained in excellent yields and enantioselectivities. Furthermore, one of the enantiopure trans-spiranes bearing an additional α-substitution on the cyclohexanone ring was then epimerized into its thermodynamically stable cis counterpart, with little loss of enantioselectivity to demonstrate the feasibility of such a transformation. Mechanistic investigations revealed two competing pathways, a concerted Diels–Alder reaction and a stepwise Michael addition, for the formation of corresponding products
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an Enantioselective synthesis of substituted cyclohexanone derivatives with an all carbon quaternary stereocenter by using an organocatalytic asymmetric domino double michael addition
2015Co-Authors: Chi Han Chen, Chia Jui Lee, Ganapuram Madhusudhan Reddy, Wenwei LinAbstract:A cinchona alkaloid-catalyzed Enantioselective Method has been developed for the synthesis of densely functionalized cyclohexanone derivatives with excellent diastereoselectivities and good enantioselectivities [diastereomeric ratio (dr) >95:5 and an enantiomeric excess (ee) value up to 86 %]. The products have an all-carbon quaternary center that contains both a cyano and ester group flanked by two vicinal tertiary stereocenters. By using a one-pot procedure, the tautomeric products were then transformed into the corresponding pyrazoles, which were obtained as single isomers in good yields.
Hu Zhang - One of the best experts on this subject based on the ideXlab platform.
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simultaneous Enantioselective determination of triadimefon and its metabolite triadimenol in edible vegetable oil by gel permeation chromatography and ultraperformance convergence chromatography tandem mass spectrometry
2015Co-Authors: Zhoulin Yao, Qiang Wang, Mei Lin, Yelong Miao, Hu ZhangAbstract:A novel, sensitive, and efficient Enantioselective Method for the determination of triadimefon and its metabolite triadimenol in edible vegetable oil, was developed by gel permeation chromatography and ultraperformance convergence chromatography/tandem triple quadrupole mass spectrometry. After the vegetable oil samples were prepared using gel permeation chromatography, the eluent was collected, evaporated, and dried with nitrogen gas. The residue was redissolved by adding methanol up to a final volume of 1 mL. The analytes of six enantiomers were analyzed on Chiralpak IA-3 column (150 × 4.6 mm) using compressed liquid CO2-mixed 14 % co-solvents, comprising methanol/acetonitrile/isopropanol = 20/20/60 (v/v/v) in the mobile phase at 30 °C, and the total separation time was less than 4 min at a flow rate of 2 mL/min. Quantification was achieved using matrix-matched standard calibration curves. The overall mean recoveries for six enantiomers from vegetable oil were 90.1-97.3 %, with relative standard deviations of 0.8-5.4 % intra-day and 2.3-5.0 % inter-day at 0.5, 5, and 50 μg/kg levels. The limits of quantification were 0.5 μg/kg for all enantiomers based on five replicate extractions at the lowest fortified level in vegetable oil. Moreover, the absolute configuration of six enantiomers had been determined based on comparisons of the vibrational circular dichroism experimental spectra with the theoretical curve obtained by density functional theory calculations. Application of the proposed Method to the 40 authentic vegetable oil samples from local markets suggests its potential use in Enantioselective determination of triadimefon and triadimenol enantiomers. Graphical Abstract Chemical structures and UPC(2)-MS/MS separation chromatograms of triadimefon and triadimenol.
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Enantioselective determination of acaricide etoxazole in orange pulp peel and whole orange by chiral liquid chromatography with tandem mass spectrometry
2015Co-Authors: Zhoulin Yao, Qiang Wang, Shulin Zhuang, Mei Lin, Hu ZhangAbstract:An efficient Enantioselective Method for the determination of etoxazole in orange pulp, peel, and whole orange was developed using liquid chromatography with tandem mass spectrometry. The enantioseparation was performed on a Chiralpak AD-3R column at 30oC using acetonitrile with 0.1% formic acid solution (80:20, v/v) as the mobile phase in less than 5 min. Quantification was achieved using matrix-matched standard calibration curves. The overall mean recoveries for two enantiomers from orange pulp and whole orange were 91.0-99.6% and the orange peel was 92.6-103.1%, with relative standard deviations of 0.8-5.4% intraday and 2.0-4.8% interday at 1, 10, and 100 μg/kg levels, and 1.3-5.2% intraday and 3.5-4.3% interday at 5, 50, and 500 μg/kg levels, respectively. The limits of quantification for all enantiomers in three matrices did not exceed 5 μg/kg. Moreover, the absolute configuration of etoxazole enantiomers had been determined by the combination of experimental and predicted electronic circular dichroism spectra, and the first eluted enantiomer was confirmed as (S)-etoxazole on a Chiralpak AD-3R column while (R)-etoxazole was first on three cellulose chiral columns. The application of the proposed Method to real sample analysis suggests its potential use in Enantioselective determination of etoxazole enantiomers in citrus.
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analysis of tebuconazole and tetraconazole enantiomers by chiral hplc ms ms and application to measure Enantioselective degradation in strawberries
2012Co-Authors: Hu Zhang, Xinquan Wang, Xiangyun Wang, Mingrong Qian, Qiang Wang, Minghua WangAbstract:A rapid and sensitive Enantioselective Method for the determination of tebuconazole and tetraconazole enantiomers in strawberry has been developed. The enantiomers were resolved by high-performance liquid chromatography on a cellulose tris (3-chloro-4-methylphenylcarbamate) (Lux Cellulose-2) column using methanol–0.1% formic acid solution (70:30, v/v) as mobile phase. The chiral liquid chromatographic separation was combined with an extract/cleanup procedure known as the quick, easy, cheap, effective, rugged, and safe (QuEChERS) Method. High-performance liquid chromatography-tandem mass spectrometry with electrospray ionization was then used for qualitative and quantitative determination of the enantiomers of tebuconazole and tetraconazole. Hexaconazole was used as an internal standard. The Method provided high selectivity and sensitivity, and the limits of quantification for tebuconazole and tetraconazole enantiomers in strawberry were both 2.5 μg/kg. The Method was successfully utilized to investigate the probable Enantioselective degradation of tebuconazole and tetraconazole in strawberry. The results showed that the degradation of the tebuconazole and tetraconazole enantiomers in strawberry followed first-order kinetics (R 2 > 0.96). The results from this study revealed the degradation of tetraconazole in strawberry was not Enantioselective, while the degradation of tebuconazole was Enantioselective, and the (+)-tebuconazole showed a faster degradation than (−)-tebuconazole in strawberry. The results could provide a reference to fully evaluate risks of these two fungicides.
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residue analysis and degradation studies of fenbuconazole and myclobutanil in strawberry by chiral high performance liquid chromatography tandem mass spectrometry
2011Co-Authors: Hu Zhang, Xinquan Wang, Xiangyun Wang, Mingrong Qian, Hao Xu, Mingfei Xu, Qiang WangAbstract:A simple and sensitive Enantioselective Method for the determination of fenbuconazole and myclobutanil in strawberry was developed by high-performance liquid chromatography–tandem mass spectrometry (HPLC-MS/MS). Fenbuconazole and myclobutanil residues in strawberry were extracted with acetonitrile containing 1% acetic acid, and an aliquot was cleaned up with PSA (primary and secondary amine) and C18 sorbent. The direct resolution of fenbuconazole and myclobutanil enantiomers was performed on a cellulose tris (3,5-dimethylphenylcarbamate) column using acetonitrile–0.1% formic acid solution (60:40, v/v) as the mobile phase. Quantification was achieved using matrix-matched standard calibration curves, and the limits of quantification for fenbuconazole and myclobutanil enantiomers in strawberry were both 2 μg/kg. The Method was successfully utilized to investigate the probable Enantioselective degradation of fenbuconazole and myclobutanil in strawberry. The results showed that the degradation of the fenbucona...
Roberto Cirilli - One of the best experts on this subject based on the ideXlab platform.
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direct hplc enantioseparation of chemopreventive chiral isothiocyanates sulforaphane and iberin on immobilized amylose based chiral stationary phases under normal phase polar organic and aqueous conditions
2020Co-Authors: Alessia Panusa, Alessia Rosetti, Claudio Villani, Roberto CirilliAbstract:Abstract Sulforaphane and iberin are promising chemopreventive chiral phytochemicals. The chirality of these organic isothiocyanates is due to the presence of a stereogenic sulfur atom. Investigations of the effectiveness of single enantiomers as chemoprotective agents highlight the key role played by sulfur chirality on biological activity. The predominant native (R)-enantiomer is active whereas the (S)-counterpart is inactive or poorly active. Here, we provide an Enantioselective Method for the direct and complete resolution of both chiral sulfoxides by high-performance liquid chromatography on immobilized amylose-derived chiral stationary phases. A set of five different columns was investigated utilizing normal-phase, polar organic and aqueous conditions. The effect of the composition of mobile phase on enantioselectivity and retention was carefully evaluated. U-shape retention maps, which are indicative of a double and competitive hydrophilic interaction liquid chromatography and reversed-phase liquid chromatography retention mechanism, were established by recording the retention factors of the enantiomers of sulforaphane on the Chiralpak IA-3 and Chiralpak IG-3 chiral stationary phases varying progressively the water content in the water-acetonitrile mobile phases.
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temperature and eluent composition effects on enantiomer separation of carvedilol by high performance liquid chromatography on immobilized amylose based chiral stationary phases
2019Co-Authors: Cristina Panella, Rosella Ferretti, Adriano Casulli, Roberto CirilliAbstract:Abstract Carvedilol is a chiral drug with potent antihypertensive and antianginal activities. Although it is clinically used as a racemic mixture, its enantiomers show different pharmacokinetic and pharmacodynamic profiles. Here, the direct chiral separation of racemic drug by high performance liquid chromatography using two immobilized-type amylose-based chiral stationary phases is presented. Some chromatographic parameters, such as retention and selectivity, were determined under multimodal eluent conditions and different temperatures. A temperature-dependent inversion of the elution order of enantiomers was observed in the operative temperature range of chiral chromatographic support. Finally, an effective direct Enantioselective Method was successfully applied to the separation of the enantiomers of carvedilol on a semipreparative scale.
Chia Jui Lee - One of the best experts on this subject based on the ideXlab platform.
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expanding the scope of primary amine catalysis stereoselective synthesis of indanedione fused 2 6 disubstituted trans spirocyclohexanones
2016Co-Authors: Madhusudhan G Reddy, Kai Hong Hsieh, Chia Jui Lee, Utpal Das, Wenwei LinAbstract:A cinchona-alkaloid-derived chiral primary-amine-catalyzed Enantioselective Method for the synthesis of the thermodynamically less stable indanedione-fused 2,6-trans-disubstituted spirocyclohexanones is demonstrated. Both the enantiomeric forms of the trans isomer are obtained in excellent yields and enantioselectivities. Furthermore, one of the enantiopure trans-spiranes bearing an additional α-substitution on the cyclohexanone ring was then epimerized into its thermodynamically stable cis counterpart, with little loss of enantioselectivity to demonstrate the feasibility of such a transformation. Mechanistic investigations revealed two competing pathways, a concerted Diels–Alder reaction and a stepwise Michael addition, for the formation of corresponding products.
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Expanding the Scope of Primary Amine Catalysis: Stereoselective Synthesis of Indanedione-Fused 2,6-Disubstituted trans-Spirocyclohexanones
2016Co-Authors: Madhusudhan G Reddy, Kai Hong Hsieh, Chia Jui Lee, Utpal Das, Wenwei LinAbstract:A cinchona-alkaloid-derived chiral primary-amine-catalyzed Enantioselective Method for the synthesis of the thermodynamically less stable indanedione-fused 2,6-trans-disubstituted spirocyclohexanones is demonstrated. Both the enantiomeric forms of the trans isomer are obtained in excellent yields and enantioselectivities. Furthermore, one of the enantiopure trans-spiranes bearing an additional α-substitution on the cyclohexanone ring was then epimerized into its thermodynamically stable cis counterpart, with little loss of enantioselectivity to demonstrate the feasibility of such a transformation. Mechanistic investigations revealed two competing pathways, a concerted Diels–Alder reaction and a stepwise Michael addition, for the formation of corresponding products
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an Enantioselective synthesis of substituted cyclohexanone derivatives with an all carbon quaternary stereocenter by using an organocatalytic asymmetric domino double michael addition
2015Co-Authors: Chi Han Chen, Chia Jui Lee, Ganapuram Madhusudhan Reddy, Wenwei LinAbstract:A cinchona alkaloid-catalyzed Enantioselective Method has been developed for the synthesis of densely functionalized cyclohexanone derivatives with excellent diastereoselectivities and good enantioselectivities [diastereomeric ratio (dr) >95:5 and an enantiomeric excess (ee) value up to 86 %]. The products have an all-carbon quaternary center that contains both a cyano and ester group flanked by two vicinal tertiary stereocenters. By using a one-pot procedure, the tautomeric products were then transformed into the corresponding pyrazoles, which were obtained as single isomers in good yields.