20585-39-1Relevant articles and documents
Isothiourea-Catalyzed Acylative Kinetic Resolution of Tertiary α-Hydroxy Esters
Greenhalgh, Mark D.,Laina-Martín, Víctor,Neyyappadath, Rifahath M.,Qu, Shen,Smith, Andrew D.,Smith, Samuel M.
supporting information, p. 16572 - 16578 (2020/09/09)
A highly enantioselective isothiourea-catalyzed acylative kinetic resolution (KR) of acyclic tertiary alcohols has been developed. Selectivity factors of up to 200 were achieved for the KR of tertiary alcohols bearing an adjacent ester substituent, with both reaction conversion and enantioselectivity found to be sensitive to the steric and electronic environment at the stereogenic tertiary carbinol centre. For more sterically congested alcohols, the use of a recently-developed isoselenourea catalyst was optimal, with equivalent enantioselectivity but higher conversion achieved in comparison to the isothiourea HyperBTM. Diastereomeric acylation transition state models are proposed to rationalize the origins of enantiodiscrimination in this process. This KR procedure was also translated to a continuous-flow process using a polymer-supported variant of the catalyst.
Intermolecular Radical Addition to Ketoacids Enabled by Boron Activation
Xie, Shasha,Li, Defang,Huang, Hanchu,Zhang, Fuyuan,Chen, Yiyun
, p. 16237 - 16242 (2019/10/14)
The intermolecular radical addition to the carbonyl group is difficult due to the facile fragmentation of the resulting alkoxyl radical. To date, the intermolecular radical addition to ketones, a valuable approach to construct quaternary carbon centers, remains a formidable synthetic challenge. Here, we report the first visible-light-induced intermolecular alkyl boronic acid addition to α-ketoacids enabled by the Lewis acid activation. The in situ boron complex formation is confirmed by various spectroscopic measurements and mechanistic probing experiments, which facilitates various alkyl boronic acid addition to the carbonyl group and prevents the cleavage of the newly formed C-C bond. Diversely substituted lactates can be synthesized from readily available alkyl boronic acids and ketoacids at room temperature merely under visible light irradiation, without any additional reagent. This boron activation approach can be extended to alkyl dihydropyridines as radical precursors with external boron reagents for primary, secondary, and tertiary alkyl radical additions. The pharmaceutically useful anticholinergic precursors are easily scaled up in multigrams under metal-free conditions in flow reactors.
Nitrilases
-
Paragraph 0495, (2015/09/22)
The invention relates to nitrilases and to nucleic acids encoding the nitrilases. In addition, methods of designing new nitrilases and methods of use thereof are also provided. The nitrilases have increased activity and stability at increased pH and temperature.
