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Your search keyword '"Brooks H."' showing total 987 results
Start Over Author "Brooks H." Publication Type Academic Journals
987 results on '"Brooks H."'

1. Designing chemical systems for precision deuteration of medicinal building blocks

Author

Jonathan D. Dabbs, Caleb C. Taylor, Martin S. Holdren, Sarah E. Brewster, Brian T. Quillin, Alvin Q. Meng, Diane A. Dickie, Brooks H. Pate, and W. Dean Harman

Subjects
Science
Abstract

Abstract Methods are lacking that can prepare deuterium-enriched building blocks, in the full range of deuterium substitution patterns at the isotopic purity levels demanded by pharmaceutical use. To that end, this work explores the regio- and stereoselective deuteration of tetrahydropyridine (THP), which is an attractive target for study due to the wide prevalence of piperidines in drugs. A series of d0–d8 tetrahydropyridine isotopomers were synthesized by the stepwise treatment of a tungsten-complexed pyridinium salt with H−/D− and H+/D+. The resulting decomplexed THP isotopomers and isotopologues were analyzed via molecular rotational resonance (MRR) spectroscopy, a highly sensitive technique that distinguishes isotopomers and isotopologues by their unique moments of inertia. In order to demonstrate the medicinal relevance of this approach, eight unique deuterated isotopologues of erythro-methylphenidate were also prepared.

Published
2024
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2. Characterization of Steel Foams for Structural Components

Author

Sanjay R. Arwade, Benjamin W. Schafer, Jerome F. Hajjar, Brooks H. Smith, and Stefan Szyniszewski

Subjects
steel foam, metal hollow sphere, experiment, tension, fracture, poisson&#8217, s ratio, panel, Mining engineering. Metallurgy, TN1-997
Abstract

Experimentally measured mechanical properties of hollow sphere steel foam are the subject of this paper. The characterization of the hollow sphere foam encompasses compressive yield stress and densification strain, compressive plastic Poisson’s ratio, and compressive unloading modulus, as well as tensile elastic modulus, tensile unloading modulus, tensile yield stress, and tensile fracture strain. Shear properties are also included. These tests provide sufficient information to allow calibration of a macroscopic, continuum constitutive model. Calibrated foam plasticity parameters are tabulated, and unique feature of foam plasticity are explained. Also, initial development of mesoscale simulations, which explicitly model voids and sintered hollow spheres, is reported. This work is part of a larger effort to help the development of steel foam as a material with relevance to civil engineering applications.

Published
2012
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5. Determining 3D structure from molecular formula and isotopologue rotational spectra in natural abundance with reflection-equivariant diffusion.

Author

Cheng, Austin H., Lo, Alston, Miret, Santiago, Pate, Brooks H., and Aspuru-Guzik, Alán

Subjects
CHEMICAL formulas, MOLECULAR structure, MOMENTS of inertia, SMALL molecules, INTERSTELLAR medium, MOMENTS method (Statistics)
Abstract

Structure determination is necessary to identify unknown organic molecules, such as those in natural products, forensic samples, the interstellar medium, and laboratory syntheses. Rotational spectroscopy enables structure determination by providing accurate 3D information about small organic molecules via their moments of inertia. Using these moments, Kraitchman analysis determines isotopic substitution coordinates, which are the unsigned |x|, |y|, |z| coordinates of all atoms with natural isotopic abundance, including carbon, nitrogen, and oxygen. While unsigned substitution coordinates can verify guesses of structures, the missing +/− signs make it challenging to determine the actual structure from the substitution coordinates alone. To tackle this inverse problem, we develop Kreed (Kraitchman REflection-Equivariant Diffusion), a generative diffusion model that infers a molecule's complete 3D structure from only its molecular formula, moments of inertia, and unsigned substitution coordinates of heavy atoms. Kreed's top-1 predictions identify the correct 3D structure with near-perfect accuracy on large simulated datasets when provided with substitution coordinates of all heavy atoms with natural isotopic abundance. Accuracy decreases as fewer substitution coordinates are provided, but is retained for smaller molecules. On a test set of experimentally measured substitution coordinates gathered from the literature, Kreed predicts the correct all-atom 3D structure in 25 of 33 cases, demonstrating experimental potential for de novo 3D structure determination with rotational spectroscopy. [ABSTRACT FROM AUTHOR]

Published
2024
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9. Designing chemical systems for precision deuteration of medicinal building blocks.

Author

Dabbs, Jonathan D., Taylor, Caleb C., Holdren, Martin S., Brewster, Sarah E., Quillin, Brian T., Meng, Alvin Q., Dickie, Diane A., Pate, Brooks H., and Harman, W. Dean

Subjects
CHEMICAL systems, ISOMERISM, DEUTERATION, MOMENTS of inertia, ISOTOPOLOGUES
Abstract

Methods are lacking that can prepare deuterium-enriched building blocks, in the full range of deuterium substitution patterns at the isotopic purity levels demanded by pharmaceutical use. To that end, this work explores the regio- and stereoselective deuteration of tetrahydropyridine (THP), which is an attractive target for study due to the wide prevalence of piperidines in drugs. A series of d0–d8 tetrahydropyridine isotopomers were synthesized by the stepwise treatment of a tungsten-complexed pyridinium salt with H−/D− and H+/D+. The resulting decomplexed THP isotopomers and isotopologues were analyzed via molecular rotational resonance (MRR) spectroscopy, a highly sensitive technique that distinguishes isotopomers and isotopologues by their unique moments of inertia. In order to demonstrate the medicinal relevance of this approach, eight unique deuterated isotopologues of erythro-methylphenidate were also prepared. Deuteration of active pharmaceutical ingredients is increasingly applied as the isosteric and isotopic replacement can modulate the pharmacokinetic profile, without necessarily having to alter the overall synthetic strategy toward the compound of interest. Here, the authors show manifold deuterations of piperidines and apply molecular rotational resonance (MRR) spectroscopy as a methodology to distinguish isotopomers within a distribution of products. [ABSTRACT FROM AUTHOR]

Published
2024
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12. Monitoring and understanding changes in heat waves, cold waves, floods, and droughts in the United States: State of knowledge

Author

Peterson, TC, Heim, RR, Hirsch, R, Kaiser, DP, Brooks, H, Diffenbaugh, NS, Dole, RM, Giovannettone, JP, Guirguis, K, Karl, TR, Katz, RW, Kunkel, K, Lettenmaier, D, McCabe, GJ, Paciorek, CJ, Ryberg, KR, Schubert, S, Silva, VBS, Stewart, BC, Vecchia, AV, Villarini, G, Vose, RS, Walsh, J, Wehner, M, Wolock, D, Wolter, K, Woodhouse, CA, and Wuebbles, D

Subjects
Meteorology & Atmospheric Sciences, Astronomical and Space Sciences, Atmospheric Sciences, Physical Geography and Environmental Geoscience
Abstract

Some of the long-term changes in weather and climate extremes across the US have occurred as expected in the warming climate, but the trends vary throughout the country and easily detected due to multiyear and decadal variations. The US National Climate Assessment has to address extremes, as these are changing and anthropogenic climate change has a role in altering the probabilities of some of the extreme events. Extreme events also drive changes in natural and human systems more than average climatic conditions. Four workshops have been held to provide technical input to the US National Climate Assessment writing team where leading scientists in the field worked jointly to determine how best to assess the state of the science in understanding the decadal- to century-scale variability and changes in various types of extreme events.

Published
2013

13. Monitoring and understanding trends in extreme storms: State of knowledge

Author

Kunkel, KE, Karl, TR, Brooks, H, Kossin, J, Lawrimore, JH, Arndt, D, Bosart, L, Changnon, D, Cutter, SL, Doesken, N, Emanuel, K, Groisman, PY, Katz, RW, Knutson, T, O'brien, J, Paciorek, CJ, Peterson, TC, Redmond, K, Robinson, D, Trapp, J, Vose, R, Weaver, S, Wehner, M, Wolter, K, and Wuebbles, D

Subjects
Astronomical and Space Sciences, Atmospheric Sciences, Physical Geography and Environmental Geoscience, Meteorology & Atmospheric Sciences
Abstract

Review of the climate science for severe convective storms, extreme precipitation, hurricanes and typhoons, and severe snowstorms and ice storms in the US shows that the ability to detect and attribute trends varies, depending on the phenomenon. A specific subset of extreme weather and climate types affecting the country is discussed to examine these extreme weather conditions. The categories of storms described were selected as they caused property damage and loss of life. The identification of an extreme occurrence was based on meteorological properties in place of the destructiveness. The primary purpose was to examine the scientific evidence for the prevailing capability to detect trends and understand their causes for certain weather types, including severe convective storms and hurricanes and typhoons.

Published
2013

16. Coordinated multiple cadaver use for minimally invasive surgical training.

Author

Blaschko, Sarah D, Brooks, H Mark, Dhuy, S Michael, Charest-Shell, Cynthia, Clayman, Ralph V, and McDougall, Elspeth M

Subjects
Humans, Cadaver, Laparoscopy, Robotics, Clinical Competence, Teaching, Minimally Invasive Surgical Procedures, Surgery, Clinical Sciences
Abstract

BackgroundThe human cadaver remains the gold standard for anatomic training and is highly useful when incorporated into minimally invasive surgical training programs. However, this valuable resource is often not used to its full potential due to a lack of multidisciplinary cooperation. Herein, we propose the coordinated multiple use of individual cadavers to better utilize anatomical resources and potentiate the availability of cadaver training.MethodsTwenty-two postgraduate surgeons participated in a robot-assisted surgical training course that utilized shared cadavers. All participants completed a Likert 4-scale satisfaction questionnaire after their training session. Cadaveric tissue quality and the quality of the training session related to this material were assessed.ResultsNine participants rated the quality of the cadaveric tissue as excellent, 7 as good, 5 as unsatisfactory, and 1 as poor. Overall, 72% of participants who operated on a previously used cadaver were satisfied with their training experience and did not perceive the previous use deleterious to their training.ConclusionThe coordinated use of cadavers, which allows for multiple cadaver use for different teaching sessions, is an excellent training method that increases availability of human anatomical material for minimally invasive surgical training.

Published
2007

18. Estimated GFR and the Effect of Intensive Blood Pressure Lowering After Acute Intracerebral Hemorrhage

Author

Anderson, C.S., Chalmers, J., Arima, H., Davis, S., Heeley, E., Huang, Y., Lavados, P., Neal, B., Parsons, M.W., Lindley, R., Morgenstern, L., Robinson, T., Stapf, C., Tzourio, C., Wang, J.G., Chen, S., Chen, X.Y., Cui, L., Liu, Z., Lu, C., Wang, J., Wu, S., Xu, E., Yang, Q., Zhang, C., Zhang, J., Beer, R., Schmutzhard, E., Redondo, P., Kaste, M., Soinne, L., Tatlisumak, T., Wartenberg, K., Ricci, S., Klijn, K., Azevedo, E., Chamorro, A., Arnold, M., Fischer, U., Kaul, S., Pandian, J., Boyini, H., Singh, S., Rabinstein, A.A., Estol, C., Silva, G., Olavarria, V.V., Robinson, T.G., Simes, R.J., Bousser, M.-G., Hankey, G., Jamrozik, K., Johnston, S.C., Li, S., Bailey, K., Cheung, T., Delcourt, C., Chintapatla, S., Ducasse, E., Erho, T., Hata, J., Holder, B., Knight, E., Leroux, M., Sassé, T., Odgers, E., Walsh, R., Wolfowicz, Z., Chen, G., Fuentes, S., Peng, B., Schneble, H.-M., Wang, M.-X., Billot, L., Heritier, S., Li, Q., Woodward, M., Abimbola, S., Anderson, S., Chan, E., Cheng, G., Chmielnik, P., Leighton, S., Liu, J.-Y., Rasmussen, B., Saxena, A., Tripathy, S., Armenis, M., Baig, M.A., Naidu, B., Starzec, G., Steley, S., Moles, A., Ruiz, A., Zimmermann, M., Marinho, J., Alves, S., Angelim, R., Araujo, J., Kawakami, L., Bustos, C., Gonzalez, F., Munoz Venturelli, P., Chen, X., Jia, R., Li, N., Qu, S., Shu, Y., Song, A., Sun, J., Xiao, J., Zhao, Y., Huang, Q., Vicaut, E., Chamam, A., Viaud, M.-C., Dert, C., Fiedler, U., Jovis, V., Kabla, S., Marchand, S., Pena, A., Rochaud, V., Mallikarjuna, K., Hasan, N., Berge, E., Sandset, E.C., Forårsveen, A.S., Richardson, D., Kumar, T., Lewin, S., Poulter, N., Field, J., Anjum, A., Wilson, A., Perelmuter, H., Agarie, A.M., Barboza, A.G., Recchia, L.A., Miranda, I.F., Rauek, S.G., Duplessis, R.J., Dewey, H., Walker, L., Petrolo, S., Bladin, C., Sturm, J., Crimmins, D., Griffiths, D., Schutz, A., Zenteno, V., Miteff, F., Spratt, N., Kerr, E., Levi, C.R., Phan, T.G., Ma, H., Sanders, L., Moran, C., Wong, K., Read, S., Henderson, R., Wong, A., Hull, R., Skinner, G., Hand, P., Yan, B., Tu, H., Campbell, B., Blacker, D.J., Wijeratne, T., Pathirage, M., Jasinararchchi, M., Matkovic, Z., Celestino, S., Gruber, F., Vosko, M.R., Diabl, E., Rathmaier, S., Pfausler, B., Helbok, R., Fazekas, F., Fischer, R., Poltrum, B., Zechner, B., Trummer, U., Rutgers, M.P., Peeters, A., Dusart, A., Duray, M.-C., Parmentier, C., Ferrao-Santos, S., Brouns, R., De Raedt, S., De Smedt, A., VanHooff, R.-J., De Keyser, J., Martins, S.C.O., de Almeida, A.G., Broudani, R., Titton, N.F., de Freitas, G.R., Cardoso, F.M., Giesel, L.M., Lima, N.A., Jr, Ferraz de Almeida, A.C., Gomes, R.B., Borges dos Santos, T.S., Veloso Soares, E.M., Neto, O.L.A., Silva, G.S., Gomes, D.L., de Carvalho, F.A., Miranda, M., Marques, A., Zétola, V.F., de Matia, G., Lange, M.C., Montes, J., Reccius, A., Soto, A., Rivas, R., Klapp, C., Illanes, S., Aguilera, C., Castro, A., Figueroa, C., Benavides, J., Salamanca, P., Concha, M.C., Pajarito, J., Araya, P., Guerra, F., Li, Y., Liu, G., Wang, B., Chong, Y., He, M., Wang, L., Liu, J., Zhang, X., Lai, C., Jiang, H., Cui, S., Tao, Q., Zhang, Y., Yao, S., Xu, M., Xiao, H., Hu, J., Tang, J., Ji, H., Jiang, M., Yu, F., Yang, X., Guo, X., Wang, Y., Wu, L., Gao, Y., Sun, D., Huang, X., Liu, L., Li, P., Jiang, Y., Li, H., Lu, H., Zhou, J., Yuan, C., Qi, X., Qiu, F., Qian, H., Wang, W., Sun, W., Li, F., Liu, R., Peng, Q., Ren, Z., Fan, C., Wang, H., Wang, T., Shi, F., Duan, C., Chen, Z., Tan, X., Zhao, Z., Chen, J., Han, T., Zhang, L., Hu, Q., Hou, Q., Zhao, X., Zeng, G., Ma, L., Wang, F., Zeng, L., Guo, Z., Fu, Y., Song, Y., Tai, L., Liu, X., Su, X., Yang, Y., Dong, R., Xu, Y., Tian, S., Cheng, S., Su, L., Xie, X., Xu, T., Geng, D., Yan, X., Fan, H., Zhao, N., Wang, S., Yang, J., Yan, M., Li, L., Li, Z., Xu, X., Lian, Y., Sun, H., Liu, D., Wang, N., Tang, Q., Han, Z., Feng, L., Cui, Y., Tian, J., Chang, H., Sun, X., Liu, C., Wen, Z., Lin, Q., Sun, L., Hu, B., Zou, M., Bao, Q., Lin, X., Zhao, L., Tian, X., Wang, X., Li, X., Hao, L., Duan, Y., Wang, R., Wei, Z., Ren, S., Ren, H., Dong, Y., Cheng, Y., Liu, W., Han, J., Zhang, Z., Zhu, J., Qian, J., Sun, Y., Liu, K., Long, F., Peng, X., Zhang, Q., Yuan, Z., Wang, C., Huang, M., He, P., You, Y., Xia, J., Zhou, L., Hou, Y., Qi, Y., Mei, L., Lu, R., Ping, L., Zhou, S., Zhang, S., Zou, R., Guo, J., Li, M., Wei, W., Curtze, S., Saarela, M., Strbian, D., Scheperjans, F., De Broucker, T., Henry, C., Cumurciuc, R., Ibos-Augé, N., Zéghoudi, A.-C., Pico, F., Dereeper, O., Simian, M.-C., Boisselier, C., Mahfoud, A., Timsit, S., Merrien, F.M., Guillon, B., Sevin, M., Herisson, F., Magne, C., Ameri, A., Cret, C., Stefanizzi, S., Klapzcynski, F., Denier, C., Sarov-Riviere, M., Reiner, P., Mawet, J., Hervé, D., Buffon, F., Touzé, E., Domigo, V., Lamy, C., Calvet, D., Pasquini, M., Alamowitch, S., Favrole, P., Muresan, I.-P., Crozier, S., Rosso, C., Pires, C., Leger, A., Deltour, S., Cordonnier, C., Henon, H., Rossi, C., Zuber, M., Bruandet, M., Tamazyan, R., Join-Lambert, C., Juettler, E., Krause, T., Maul, S., Endres, M., Jungehulsing, G.J., Hennerici, M., Griebe, M., Sauer, T., Knoll, K., Huber, R., Knauer, K., Knauer, C., Raubold, S., Schneider, H., Hentschel, H., Lautenschläger, C., Schimmel, E., Dzialowski, I., Foerch, C., Lorenz, M., Singer, O., Meyer dos Santos, I.M.R., Hartmann, A., Hamann, A., Schacht, A., Schrader, B., Teíchmann, A., Wartenberg, K.E., Mueller, T.J., Jander, S., Gliem, M., Boettcher, C., Rosenkranz, M., Beck, C., Otto, D., Thomalla, G., Cheng, B., Wong, K.S., Leung, T.W., Soo, Y.O.Y., Prabhakar, S., Kesavarapu, S.R., Gajjela, P.K., Chenna, R.R., Ummer, K., Basheer, M., Andipet, A., Jagarlapudi, M.K.M., Mohammed, A.U.R., Pawar, V.G., Eranki, S.S.K., Singh, Y., Akhtar, N., Borah, N.C., Ghose, M., Choudhury, N., Ichaporia, N.R., Shendge, J., Khese, S., Pamidimukkala, V., Inbamuthaiah, P., Nuthakki, S.R., Tagallamudi, N.M.R., Gutti, A.K., Khurana, D., Kesavarapu, P., Jogi, V., Garg, A., Samanta, D., Sarma, G.R.K., Nadig, R., Mathew, T., Anandan, M.A., Caterbi, E., Zini, A., Cavazzuti, M., Casoni, F., Pentore, R., Falzone, F., Mazzoli, T., Greco, L.M., Menichetti, C., Coppola, F., Cenciarelli, S., Gallinella, E., Mattioni, A., Condurso, R., Sicilia, I., Zampolini, M., Corea, F., Barbi, M., Proietti, C., Toni, D., Pieroni, A., Anzini, A., Falcou, A., Demichele, M., Klijn, C.J.M., Tveiten, A., Thortveit, E.T., Pettersen, S., Holand, N., Hitland, B., Johnsen, S.H., Eltoft, A., Wasay, M., Kamal, A., Iqrar, A., Ali, L., Begum, D., Gama, G., Fonseca, L., Moreira, G., Veloso, L.M., Pinheiro, D., Paredes, L., Rozeira, C., Gregorio, T., Segura Martin, T., Ayo, O., Garcia-Garcia, J., Feria Vilar, I., Gómez Fernández, I., Amaro, S., Urra, X., Obach, V., Cervera, A., Silva, Y., Serena, J., Castellanos, M., Terceno, M., Van Eendenburg, C., Weck, A., Findling, O., Lüdi, R., Warburton, E.A., Day, D., Butler, N., Bumanlag, E., Caine, S., Steele, A., Osborn, M., Dodd, E., Murphy, P., Esisi, B., Brown, E., Hayman, R., Baliga, V.K.V., Minphone, M., Kennedy, J., Reckless, I., Pope, G., Teal, R., Michael, K., Manawadu, D., Kalra, L., Lewis, R., Mistry, B., Cattermole, E., Hassan, A., Mandizvidza, L., Bamford, J., Brooks, H., Bedford, C., Whiting, R., Baines, P., Hussain, M., Harvey, M., Fotherby, K., McBride, S., Bourke, P., Morgan, D., Jennings-Preece, K., Price, C., Huntley, S., Riddell, V.E., Storey, G., Lakey, R.L., Subramanian, G., Jenkinson, D., Kwan, J., David, O., Tiwari, D., James, M., Keenan, S., Eastwood, H., Shaw, L., Kaye, P., Button, D., Madigan, B., Williamson, D., Dixit, A., Davis, J., Hossain, M.O., Ford, G.A., Parry-Jones, A., O'Loughlin, V., Jarapa, R., Naing, Z., Lovelock, C., O'Reilly, J., Khan, U., Bhalla, A., Rudd, A., Birns, J., Werring, D.J., Law, R., Perry, R., Jones, I., Erande, R., Roffe, C., Natarajan, I., Ahmad, N., Finney, K., Lucas, J., Mistri, A., Eveson, D., Marsh, R., Haunton, V., Fugate, J.E., Lepore, S.W., Zheng, Danni, Sato, Shoichiro, Arima, Hisatomi, Heeley, Emma, Delcourt, Candice, Cao, Yongjun, Chalmers, John, and Anderson, Craig S.

Published
2016
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23. Assignment of the absolute configuration of molecules that are chiral by virtue of deuterium substitution using chiral tag molecular rotational resonance spectroscopy.

Author

Vang, Zoua Pa, Sonstrom, Reilly E., Scolati, Haley N., Clark, Joseph R., and Pate, Brooks H.

Subjects
DEUTERIUM, CHEMICAL reactions, MICROWAVE spectroscopy, SPECTROMETRY, MOLECULAR spectroscopy, RESONANCE, MOLECULES
Abstract

Chiral tag molecular rotational resonance (MRR) spectroscopy is used to assign the absolute configuration of molecules that are chiral by virtue of deuterium substitution. Interest in the improved performance of deuterated active pharmaceutical ingredients has led to the development of precision deuteration reactions. These reactions often generate enantioisotopomer reaction products that pose challenges for chiral analysis. Chiral tag rotational spectroscopy uses noncovalent derivatization of the enantioisotopomer to create the diastereomers of the 1:1 molecular complexes of the analyte and a small, chiral molecule. Assignment of the absolute configuration requires high‐confidence determinations of the structures of these weakly bound complexes. A general search method, CREST, is used to identify candidate geometries. Subsequent geometry optimization using dispersion corrected density functional theory gives equilibrium geometries with sufficient accuracy to identify the isomers of the chiral tag complexes produced in the pulsed jet expansion used to introduce the sample into the MRR spectrometer. Rotational constant scaling based on the fact that the diastereomers have the same equilibrium geometry gives accurate predictions allowing identification of the homochiral and heterochiral tag complexes and, therefore, assignment of absolute configuration. The method is successfully applied to three oxygenated substrates from enantioselective Cu‐catalyzed alkene transfer hydrodeuteration reaction chemistry. [ABSTRACT FROM AUTHOR]

Published
2023
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30. Analysis of isomeric mixtures by molecular rotational resonance spectroscopy.

Author

Neill, Justin L., Evangelisti, Luca, and Pate, Brooks H.

Subjects
COMPUTATIONAL chemistry, MOLECULAR structure, CHEMICAL reactions, RESONANCE, SPECTROMETRY, MIXTURES
Abstract

Recent developments in molecular rotational resonance (MRR) spectroscopy that have enabled its use as an analytical technique for the precise determination of molecular structure are reviewed. In particular, its use in the differentiation of isomeric compounds—including regioisomers, stereoisomers and isotopic variants—is discussed. When a mixture of isomers, such as resulting from a chemical reaction, is analyzed, it is highly desired to be able to unambiguously identify the structures of each of the components present, as well as quantify them, without requiring complex sample preparation or reference standards. MRR offers unique capabilities for addressing this analytical challenge, owing to two factors: its high sensitivity to a molecule's structure and its high spectral resolution, allowing mixtures to be resolved without separation of components. This review introduces core theoretical principles, an introduction to MRR instrumentation and the methods by which spectra can be interpreted with the aid of computational chemistry to correlate the observed patterns to molecular structures. Recent articles are discussed in which this technique was applied to help chemists complete challenging isomer analyses. Developments in the use of MRR for chiral analysis and in the measurement of isotopically labeled compounds are also highlighted. [ABSTRACT FROM AUTHOR]

Published
2023
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49. Accuracy of quantum chemistry structures of chiral tag complexes and the assignment of absolute configuration.

Author

Mayer, Kevin, West, Channing, Marshall, Frank E., Sedo, Galen, Grubbs, Garry S., Evangelisti, Luca, and Pate, Brooks H.

Abstract

The absolute configuration of a molecule can be established by analysis of molecular rotational spectra of the analyte complexed with a small chiral molecule of known configuration. This approach of converting the analyte enantiomers, with identical rotational spectra, into diastereomers that can be distinguished spectroscopically is analogous to chiral derivatization in nuclear magnetic resonance (NMR) spectroscopy. For the rotational chiral tag method, the derivatization uses noncovalent interactions to install the new chiral center and avoids complications due to possible racemization of the analyte when covalent chemistry is used. The practical success of this method rests on the ability to attribute assigned rotational spectra to specific geometries of the diastereomeric homochiral and heterochiral tag complexes formed in the pulsed jet expansion that is used to introduce samples into the microwave spectrometer. The assignment of a molecular structure to an experimental rotational spectrum uses quantum chemistry equilibrium geometries to provide theoretical estimates of the spectrum parameters that characterize the rotational spectrum. This work reports the results of a high-sensitivity rotational spectroscopy study of the complexes formed between (3)-butyn-2-ol and verbenone. The rotational spectra of four homochiral and four heterochiral complexes are assigned. In addition, the 14 distinct, singly-substituted 13C isotopomer spectra of five of these species are assigned in natural abundance. Analysis of these spectra provides direct structural characterization of the complexes through determination of the carbon atom position coordinates. This data set is used to benchmark quantum chemistry calculations of candidate equilibrium geometries of the chiral tag complexes. The quantum chemistry calculations are limited to methods commonly used in the field of rotational spectroscopy. It is shown that the accuracy of the structures from quantum chemistry provides a high-confidence assignment of cluster geometries to the observed spectra. As a result, a high-confidence determination of the analyte (verbenone) absolute configuration is achieved. [ABSTRACT FROM AUTHOR]

Published
2022
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