- Palladium Catalyzed Monoselective α-Arylation of Sulfones and Sulfonamides with 2,2,6,6-Tetramethylpiperidine·ZnCl·LiCl Base and Aryl Bromides
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A palladium catalyzed Negishi-type α-arylation of sulfones and sulfonamides with a broad range of aryl bromides has been developed. The substrates are selectively metalated in situ with tmp·ZnCl·LiCl base (tmp: 2,2,6,6-tetramethylpiperidine) and cross-coupled in the presence of a catalyst system that is generated from Pd(dba)2 and XPhos. Electron-deficient, electron-rich, and heterocyclic aryl bromides have been successfully cross-coupled, and sensitive functional groups are well tolerated. Simple aryl bromides are converted overnight at 60 °C in THF while heteroaryl bromides are efficiently coupled within 2 h at 130 °C in a microwave reactor. The desired monoarylated α-branched benzyl sulfones and sulfonamides were obtained in good yields, and overarylation was not detected. The procedure is ideal for late stage functionalization in parallel medicinal chemistry.
- Knauber, Thomas,Tucker, Joseph
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p. 5636 - 5648
(2016/07/14)
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- Extreme synergistic mutational effects in the directed evolution of a baeyer-villiger monooxygenase as catalyst for asymmetric sulfoxidation
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Structure-based directed evolution utilizing iterative saturation mutagenesis (ISM) has been applied to phenyl acetone monooxygenase (PAMO), a thermally robust Baeyer-Villiger monooxygenase, in the quest to access a mutant which displays reversed enantioselectivity in the asymmetric sulfoxidation of prochiral thioethers. Whereas WT PAMO leads to 90% ee in the sulfoxidation of p-methylbenzyl methyl thioether with preference for the (S)-sulfoxide, the evolved mutant I67Q/P440F/A442N/L443I is 95% (R)-selective in the reaction of this and other thioethers. Partial deconvolution of the (R)-selective mutant with generation of the respective four single mutants shows that all of them are (S)-selective, which points to pronounced synergism (cooperative nonadditivity) when they interact in concert. Complete deconvolution with formation of all combinatorial forms of the respective double and triple mutants allows the designed construction of a fitness landscape featuring all 24 upward pathways leading from WT to the (R)-selective quadruple mutant. In all 24 trajectories strong cooperative mutational effects were found as well, which indicates that such mutational changes in enzymes constitute nonlinear systems. A theoretical analysis based on induced fit docking explains many of the observed effects on a molecular level.
- Zhang, Zhi-Gang,Lonsdale, Richard,Sanchis, Joaquin,Reetz, Manfred T.
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p. 17262 - 17272
(2015/02/19)
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- Directed evolution of cyclohexanone monooxygenases: Enantioselective biocatalysts for the oxidation of prochiral thioethers
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Mutational changes in cyclohexanone monooxygenases (CHMOs), for example the introduction of serine at position 432, lead to surprisingly versatile enantioselective biocatalysts that perform particularly well in the air-mediated partial oxidation of prochi
- Reetz, Manfred T.,Daligault, Franck,Brunner, Birgit,Hinrichs, Heike,Deege, Alfred
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p. 4078 - 4081
(2007/10/03)
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- Azetidine derivatives, their preparation and medicaments containing them
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The invention concerns compounds of formula (1) wherein: R represents a chain (A) or (B); R1 is methyl or ethyl; R2 is either an optionally substituted aromatic or an optionally substituted heteroaromatic ring; R3 and R4, identical or different, are either an optionally substituted aromatic or an optionally substituted heteroaromatic ring; R′ represents a hydrogen atom or a —CO—alk radical, their optical isomers, their salts, their preparation and medicines containing them.
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- BIOTRANSFORMATION OF ORGANIC SULFIDES. PART 6. FORMATION OF CHIRAL para-SUBSTITUTED BENZYL METHYL SULFOXIDES BY HELMINTHOSPORIUM SPECIES NRRL 4671
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The fungus Helminthosporium species NRRL 4671 has been used for the biotransformation of a series of para-substituted benzyl sulfides with substituent groups consisting of trifluoromethyl, halo, hydroxy, methoxy, acetoxy, nitro, cyano, amino, acetamido, acyl and carboxylic acid units.In all cases, sulfoxide formation occurred in good yoeld and with predominant (S) chirality at the sulfur position.A minor amount of sulfone product was also obtained from the halo- and methoxy-substituted substrates.
- Holland, Herbert L.,Brown, Frances M.,Larsen, Brett G.
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p. 1561 - 1568
(2007/10/02)
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- Biotransformation of organic sulfides. Part 5. Formation of chiral para- alkyl benzyl methyl sulfoxides by Helminthosporium species NRRL 4671
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The fungus Helminthosporium species NRRL 4671 has been used for the biotransformation of a series of para-alkylbenzyl sulfides with alkyl groups consisting of methyl, ethyl, n.propyl, isopropyl, n.butyl, and t.butyl. For the majority of substrates, sulfox
- Holland,Brown,Larsen
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p. 1241 - 1248
(2007/10/02)
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