78800-68-7Relevant academic research and scientific papers
Asymmetric Transfer Hydrogenation of α-Keto Amides; Highly Enantioselective Formation of Malic Acid Diamides and α-Hydroxyamides
Gediya, Shweta K.,Vyas, Vijyesh K.,Clarkson, Guy J.,Wills, Martin
supporting information, p. 7803 - 7807 (2021/10/20)
The asymmetric transfer hydrogenation (ATH) of α-keto-1,4-diamides using a tethered Ru/TsDPEN catalyst was achieved in high ee. Studies on derivatives identified the structural elements which lead to the highest enantioselectivities in the products. The α-keto-amide reduction products have been converted to a range of synthetically valuable derivatives.
PD(II)-CATALYZED ENANTIOSELECTIVE C-H ARYLATION OF FREE CARBOXYLIC ACIDS
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Page/Page column 16-17, (2019/11/12)
The invention includes procedures for stereoselective β-arylation of carboxylic acids having a β-carbon atom. For example, stereoselective arylation procedures include the following reactions: (I)
Pd(II)-Catalyzed Enantioselective C(sp3)-H Arylation of Free Carboxylic Acids
Shen, Peng-Xiang,Hu, Liang,Shao, Qian,Hong, Kai,Yu, Jin-Quan
supporting information, p. 6545 - 6549 (2018/05/23)
A monoprotected aminoethyl amine chiral ligand based on an ethylenediamine backbone was developed to achieve Pd-catalyzed enantioselective C(sp3)-H arylation of cyclopropanecarboxylic and 2-aminoisobutyric acids without using exogenous directing groups. This new chiral catalyst affords new disconnection for preparing diverse chiral carboxylic acids from simple starting materials that are complementary to the various ring forming approaches.
Diversity of Secondary Structure in Catalytic Peptides with β-Turn-Biased Sequences
Metrano, Anthony J.,Abascal, Nadia C.,Mercado, Brandon Q.,Paulson, Eric K.,Hurtley, Anna E.,Miller, Scott J.
supporting information, p. 492 - 516 (2017/02/23)
X-ray crystallography has been applied to the structural analysis of a series of tetrapeptides that were previously assessed for catalytic activity in an atroposelective bromination reaction. Common to the series is a central Pro-Xaa sequence, where Pro is either l- or d-proline, which was chosen to favor nucleation of canonical β-turn secondary structures. Crystallographic analysis of 35 different peptide sequences revealed a range of conformational states. The observed differences appear not only in cases where the Pro-Xaa loop-region is altered, but also when seemingly subtle alterations to the flanking residues are introduced. In many instances, distinct conformers of the same sequence were observed, either as symmetry-independent molecules within the same unit cell or as polymorphs. Computational studies using DFT provided additional insight into the analysis of solid-state structural features. Select X-ray crystal structures were compared to the corresponding solution structures derived from measured proton chemical shifts, 3J-values, and 1H-1H-NOESY contacts. hese findings imply that the conformational space available to simple peptide-based catalysts is more diverse than precedent might suggest. The direct observation of multiple ground state conformations for peptides of this family, as well as the dynamic processes associated with conformational equilibria, underscore not only the challenge of designing peptide-based catalysts, but also the difficulty in predicting their accessible transition states. These findings implicate the advantages of low-barrier interconversions between conformations of peptide-based catalysts for multistep, enantioselective reactions.
Asymmetric hydroazidation of α-substituted vinyl ketones catalyzed by chiral primary amine
Xue, Zai-Kun,Fu, Nian-Kai,Luo, San-Zhong
supporting information, p. 1083 - 1086 (2017/05/22)
We report herein the first example of asymmetric hydroazidation of α-substituted vinyl ketones by using chiral primary amines as the catalysts. A simple chiral primary-tertiary diamine catalyst derived from L-phenylalanine was found to readily promote this aza-Michael addition reaction with enamine protonation as the key stereogenic step, thus enabling the effective synthesis of α-chiral β-azido ketones with good yields and moderate enantioselectivities.
DERIVATIVES OF DOLASTATIN 10 AND USES THEREOF
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Page/Page column 42; 43, (2016/12/22)
Derivatives of dolastatin 10 and uses thereof, the structures of which are shown as formula I, II, III and IV are provided.
Structural studies of β-turn-containing peptide catalysts for atroposelective quinazolinone bromination
Metrano,Abascal,Mercado,Paulson,Miller
supporting information, p. 4816 - 4819 (2016/04/09)
We describe herein a crystallographic and NMR study of the secondary structural attributes of a β-turn-containing tetra-peptide, Boc-Dmaa-d-Pro-Acpc-Leu-NMe2, which was recently reported as a highly effective catalyst in the atroposelective bromination of 3-arylquinazolin-4(3H)-ones. Inquiries pertaining to the functional consequences of residue substitutions led to the discovery of a more selective catalyst, Boc-Dmaa-d-Pro-Acpc-Leu-OMe, the structure of which was also explored. This new lead catalyst was found to exhibit a type I′ β-turn secondary structure both in the solid state and in solution, a structure that was shown to be an accessible conformation of the previously reported catalyst, as well.
Enantioselective Synthesis of 3-Arylquinazolin-4(3H)-ones via Peptide-Catalyzed Atroposelective Bromination
Diener, Matthew E.,Metrano, Anthony J.,Kusano, Shuhei,Miller, Scott J.
supporting information, p. 12369 - 12377 (2015/10/12)
We report the development of a tertiary amine-containing β-turn peptide that catalyzes the atroposelective bromination of pharmaceutically relevant 3-arylquinazolin-4(3H)-ones (quinazolinones) with high levels of enantioinduction over a broad substrate scope. The structure of the free catalyst and the peptide-substrate complex were explored using X-ray crystallography and 2D-NOESY experiments. Quinazolinone rotational barriers about the chiral anilide axis were also studied using density functional theory calculations and are discussed in light of the high enantioselectivities observed. Mechanistic studies also suggest that the initial bromination event is stereodetermining, and the major monobromide intermediate is an atropisomerically stable, mono-ortho-substituted isomer. The observation of stereoisomerically stable monobromides stimulated the conversion of the tribromide products to other atropisomerically defined products of interest. For example, (1) a dehalogenation Suzuki-Miyaura cross-coupling sequence delivers ortho-arylated derivatives, and (2) a regioselective Buchwald-Hartwig amination procedure installs para-amine functionality. Stereochemical information was retained during these subsequent transformations.
Peptide-catalyzed conversion of racemic oxazol-5(4 H)-ones into enantiomerically enriched α-amino acid derivatives
Metrano, Anthony J.,Miller, Scott J.
, p. 1542 - 1554 (2014/03/21)
We report the development and optimization of a tetrapeptide that catalyzes the methanolytic dynamic kinetic resolution of oxazol-5(4H)-ones (azlactones) with high levels of enantioinduction. Oxazolones possessing benzylic-type substituents were found to perform better than others, providing methyl ester products in 88:12 to 98:2 er. The mechanism of this peptide-catalyzed process was investigated through truncation studies and competition experiments. High-field NOESY analysis was performed to elucidate the solution-phase structure of the peptide, and we present a plausible model for catalysis.
Novel bifunctional thiourea-ammonium salt catalysts derived from amino acids: Application to highly enantio- and diastereoselective aza-Henry reaction
Wang, Hong-Yu,Chai, Zhuo,Zhao, Gang
supporting information, p. 5104 - 5111 (2013/06/27)
The development of new efficient and easily accessible catalysts has been one of the focuses in asymmetric phase-transfer catalysis. In this paper, a novel class of chiral bifunctional thiourea-ammonium phase-transfer catalysts were synthesized from commercially available α-amino acids. The structural modularity of these catalysts permits facile tunings to achieve optimum results, which was demonstrated in catalyzing the aza-Henry reaction with excellent enantioselectivities (up to 99.5% ee) and diastereoselectivities (up to >25:1 dr).
