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Author Razvan Simionescu

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Chemoenzymatic Total Synthesis of ent-Oxycodone: Second-, Third-, and Fourth-Generation Strategies.

Mariia Makarova, Mary Ann A Endoma-Arias, Helen E Dela Paz, Razvan Simionescu, Tomas Hudlicky,

Four distinct approaches to ent-oxycodone were designed and accomplished. All rely on the same starting material, the diene diol derived from phenethyl acetate by the whole-cell fermentation with E. coli JM109 (pDTG601A), a strain that overexpresses toluene dioxygenase. The key step in the first-generation approach involves the construction of the ... Read more >>

J Am Chem Soc (Journal of the American Chemical Society)
[2019, 141(27):10883-10904]

Cited: 1 time

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The assembly of (+)-vincadifformine- and (-)-tabersonine-derived monoterpenoid indole alkaloids in Catharanthus roseus involves separate branch pathways.

Danielle Williams, Yang Qu, Razvan Simionescu, Vincenzo De Luca,

The biological activity of monoterpenoid indole alkaloids (MIAs) has led to their use in cancer treatment and other medical applications. Their biosynthesis has involved the formation of reactive intermediates by responsible enzymes to elaborate several different chemical scaffolds. Modification of scaffolds through different substitution reactions has produced chemically diverse MIAs ... Read more >>

Plant J (The Plant journal : for cell and molecular biology)
[2019, 99(4):626-636]

Cited: 0 times

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Solution of the multistep pathway for assembly of corynanthean, strychnos, iboga, and aspidosperma monoterpenoid indole alkaloids from 19E-geissoschizine.

Yang Qu, Michael E A M Easson, Razvan Simionescu, Josef Hajicek, Antje M K Thamm, Vonny Salim, Vincenzo De Luca,

Monoterpenoid indole alkaloids (MIAs) possess a diversity of alkaloid skeletons whose biosynthesis is poorly understood. A bioinformatic search of candidate genes, combined with their virus-induced gene silencing, targeted MIA profiling and in vitro/in vivo pathway reconstitution identified and functionally characterized six genes as well as a seventh enzyme reaction required ... Read more >>

Proc Natl Acad Sci U S A (Proceedings of the National Academy of Sciences of the United States of America)
[2018, 115(12):3180-3185]

Cited: 9 times

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A Formal Approach to Xylosmin and Flacourtosides E and F: Chemoenzymatic Total Synthesis of the Hydroxylated Cyclohexenone Carboxylic Acid Moiety of Xylosmin.

Mukund Ghavre, Jordan Froese, Brennan Murphy, Razvan Simionescu, Tomas Hudlicky,

The hydroxylated cyclohexenone carboxylic acid moiety of xylosmin was synthesized in eight steps from benzoic acid. The key steps in the synthesis involved the enzymatic dihydroxylation of benzoic acid by the whole cell fermentation with Ralstonia eutrophus B9, and Henbest epoxidation. Early attempts led to the synthesis of a C6 ... Read more >>

Org Lett (Organic letters)
[2017, 19(5):1156-1159]

Cited: 2 times

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Crystal structure and solvent-dependent behaviours of 3-amino-1,6-diethyl-2,5,7-trimethyl-4,4-di-phenyl-3a,4a-di-aza-4-bora-s-indacene.

Lijing Yang, Brett Drew, Ravi Shekar Yalagala, Rameez Chaviwala, Razvan Simionescu, Alan J Lough, Hongbin Yan,

In the title compound (3-amino-4,4-diphenyl-BODIPY), C28H32BN3, the central six-membered ring has a flattened sofa conformation, with one of the N atoms deviating by 0.142 (4) Å from the mean plane of the other five atoms, which have an r.m.s. deviation of 0.015 Å. The dihedral angle between the two essentially planar outer five-membered ... Read more >>

Acta Crystallogr E Crystallogr Commun (Acta crystallographica. Section E, Crystallographic communications)
[2017, 73(Pt 3):378-382]

Cited: 0 times

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Chemoenzymatic Total Synthesis of Hydromorphone by an Oxidative Dearomatization/Intramolecular [4 + 2] Cycloaddition Sequence: A Second-Generation Approach.

Lukas Rycek, John J Hayward, Marwa Abdel Latif, James Tanko, Razvan Simionescu, Tomas Hudlicky,

A second-generation approach to the synthesis of hydromorphone by oxidative dearomatization/Diels-Alder cycloaddition was investigated. Detailed analysis of the stereochemical outcome of the [4 + 2] cycloaddition was performed first on a truncated model system as well as on the material leading to ent-hydromorphone. The stereochemical assignments were made by NMR ... Read more >>

J Org Chem (The Journal of organic chemistry)
[2016, 81(22):10930-10941]

Cited: 3 times

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Completion of the seven-step pathway from tabersonine to the anticancer drug precursor vindoline and its assembly in yeast.

Yang Qu, Michael L A E Easson, Jordan Froese, Razvan Simionescu, Tomas Hudlicky, Vincenzo De Luca,

Antitumor substances related to vinblastine and vincristine are exclusively found in the Catharanthus roseus (Madagascar periwinkle), a member of the Apocynaceae plant family, and continue to be extensively used in cancer chemotherapy. Although in high demand, these valuable compounds only accumulate in trace amounts in C. roseus leaves. Vinblastine and ... Read more >>

Proc Natl Acad Sci U S A (Proceedings of the National Academy of Sciences of the United States of America)
[2015, 112(19):6224-6229]

Cited: 50 times

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Unusual structure, fluxionality, and reaction mechanism of carbonyl hydrosilylation by silyl hydride complex [(ArN=)Mo(H)(SiH2Ph)(PMe3)3].

Andrey Y Khalimon, Stanislav K Ignatov, Andrey I Okhapkin, Razvan Simionescu, Lyudmila G Kuzmina, Judith A K Howard, Georgii I Nikonov,

The reactions of bis(borohydride) complexes [(RN=)Mo(BH4)2(PMe3)2] (4: R = 2,6-Me2C6H3; 5: R = 2,6-iPr2C6H3) with hydrosilanes afford new silyl hydride derivatives [(RN=)Mo(H)(SiR'3)(PMe3)3] (3: R = Ar, R'3 = H2Ph; 8: R = Ar', R'3 = H2Ph; 9: R = Ar, R'3 = (OEt)3; 10: R = Ar, R'3 = HMePh). ... Read more >>

Chemistry (Chemistry (Weinheim an der Bergstrasse, Germany))
[2013, 19(26):8573-8590]

Cited: 2 times

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A detailed NMR- and DFT-based study of the Sakurai-Hosomi-Yamamoto asymmetric allylation reaction.

David Hurem, Andrey G Moiseev, Razvan Simionescu, Travis Dudding,

A Lewis acid complex between benzaldehyde and the silver catalyst was detected by (31)P NMR and shown to be the direct precursor to allylation within the Sakurai-Hosomi-Yamamoto reaction. Structural and thermochemical hybrid-DFT calculations indicated that benzaldehyde predominantly formed an η(1)-σ-complex with the catalyst; however, two other competing conformers involving different ... Read more >>

J Org Chem (The Journal of organic chemistry)
[2013, 78(9):4440-4445]

Cited: 1 time

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Observation of two N2-isobutyrylguanine tautomers by NMR spectroscopy.

Lijing Yang, Jia Li, Razvan Simionescu, Hongbin Yan,

N(2)-isobutyrylguanine was prepared by treatment of guanine with isobutyryl chloride. Two tautomers, 1,7-dihydro-2-(isobutyroyl)amino-6H-purin-6-one and 1,9-dihydro-2-(isobutyroyl)amino-6H-purin-6-one, were identified in almost 1:1 ratio in dichloromethane-dimethyl sulfoxide (1:1 v/v) by NMR spectroscopy. By using the selective-inversion experiments, enthalpy, entropy, and free energy for activation were determined. This work represents the first report of guanine ... Read more >>

Magn Reson Chem (Magnetic resonance in chemistry : MRC)
[2013, 51(1):60-64]

Cited: 0 times

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Mechanistic aspects of hydrosilylation catalyzed by (ArN=)Mo(H)(Cl)(PMe3)3.

Andrey Y Khalimon, Oleg G Shirobokov, Erik Peterson, Razvan Simionescu, Lyudmila G Kuzmina, Judith A K Howard, Georgii I Nikonov,

The reaction of (ArN=)MoCl(2)(PMe(3))(3) (Ar = 2,6-diisopropylphenyl) with L-Selectride gives the hydrido-chloride complex (ArN=)Mo(H)(Cl)(PMe(3))(3) (2). Complex 2 was found to catalyze the hydrosilylation of carbonyls and nitriles as well as the dehydrogenative silylation of alcohols and water. Compound 2 does not show any productive reaction with PhSiH(3); however, a slow ... Read more >>

Inorg Chem (Inorganic chemistry)
[2012, 51(7):4300-4313]

Cited: 10 times

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An unexpected mechanism of hydrosilylation by a silyl hydride complex of molybdenum.

Andrey Y Khalimon, Stanislav K Ignatov, Razvan Simionescu, Lyudmila G Kuzmina, Judith A K Howard, Georgii I Nikonov,

Carbonyl hydrosilylation catalyzed by (ArN)Mo(H)(SiH(2)Ph)(PMe(3))(3) (3) is unusual in that it does not involve the expected Si-O elimination from intermediate (ArN)Mo(SiH(2)Ph)(O(i)Pr)(PMe(3))(2) (7). Instead, 7 reversibly transfers β-CH hydrogen from the alkoxide ligand to metal. ... Read more >>

Inorg Chem (Inorganic chemistry)
[2012, 51(2):754-756]

Cited: 4 times

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Catalytic and stoichiometric reactivity of β-silylamido agostic complex of Mo: intermediacy of a silanimine complex and applications to multicomponent coupling.

Andrey Y Khalimon, Razvan Simionescu, Georgii I Nikonov,

The reaction of complex (ArN═)(2)Mo(PMe(3))(3) (Ar = 2,6-diisopropylphenyl) with PhSiH(3) gives the β-agostic NSi-H···M silyamido complex (ArN═)Mo(SiH(2)Ph)(PMe(3))(η(3)-ArN-SiHPh-H) (3) as the first product. 3 decomposes in the mother liquor to a mixture of hydride compounds, including complex {η(3)-SiH(Ph)-N(Ar)-SiHPh-H···}MoH(3)(PMe(3))(3) characterized by NMR. Compound 3 was obtained on preparative scale by reacting (ArN═)(2)Mo(PMe(3))(3) ... Read more >>

J. Am. Chem. Soc. (Journal of the American Chemical Society)
[2011, 133(18):7033-7053]

Cited: 11 times

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The unexpected mechanism of carbonyl hydrosilylation catalyzed by (Cp)(ArN[double bond, length as m-dash])Mo(H)(PMe(3)).

Oleg G Shirobokov, Serge I Gorelsky, Razvan Simionescu, Lyudmila G Kuzmina, Georgii I Nikonov,

Complex (Cp)(ArN[double bond, length as m-dash])Mo(H)(PMe(3)) (2, Ar = 2,6-diisopropylphenyl) catalyzes the hydrosilylation of carbonyls by an unexpected associative mechanism. Complex 2 also reacts with PhSiH(3) by a σ-bond metathesis mechanism to give the silyl derivative (Cp)(ArN[double bond, length as m-dash])Mo(SiH(2)Ph)(PMe(3)). ... Read more >>

Chem. Commun. (Camb.) (Chemical communications (Cambridge, England))
[2010, 46(41):7831-7833]

Cited: 6 times

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Design of thermally stable versions of the burgess reagent: stability and reactivity study.

Thomas A Metcalf, Razvan Simionescu, Tomas Hudlicky,

Three new versions of the Burgess reagent were synthesized and their thermal stability investigated by NMR. The new reagents exhibited improved reactivity toward epoxides, diols, and vinyl oxiranes as compared with the original version. ... Read more >>

J Org Chem (The Journal of organic chemistry)
[2010, 75(10):3447-3450]

Cited: 0 times

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Diversity of catalysis by an imido-hydrido complex of molybdenum. Mechanism of carbonyl hydrosilylation and silane alcoholysis.

Erik Peterson, Andrey Y Khalimon, Razvan Simionescu, Lyudmila G Kuzmina, Judith A K Howard, Georgii I Nikonov,

New Imido hydride complex 1 catalyzes a variety of silylation reactions that proceed via initial substrate activation but not silane addition. ... Read more >>

J. Am. Chem. Soc. (Journal of the American Chemical Society)
[2009, 131(3):908-909]

Cited: 15 times

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Assignment of the 1H and 13C NMR of tocotrienols.

Stephan Ohnmacht, Ryan West, Razvan Simionescu, Jeffrey Atkinson,

Vitamin E is a family of chromanols that vary by the degree of methylation of the chroman ring as well as the nature of the hydrophobic side chain at C2 that serves to anchor these lipids in biological membranes. The tocopherols contain saturated side chains, whereas the tocotrienols contain three ... Read more >>

Magn Reson Chem (Magnetic resonance in chemistry : MRC)
[2008, 46(3):287-294]

Cited: 9 times

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Agostic NSi-H...Mo complexes: from curiosity to catalysis.

Andrey Y Khalimon, Razvan Simionescu, Lyudmila G Kuzmina, Judith A K Howard, Georgii I Nikonov,

Angew. Chem. Int. Ed. Engl. (Angewandte Chemie (International ed. in English))
[2008, 47(40):7701-7704]

Cited: 10 times

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