Using Garner's aldehyde as a substrate, one-pot MAC hydroxyhomologation reactions proceeded in good yields and with anti selectivity for the first time (dr up to 9:1). The products were used to prepare a panel of protected derivatives of erythro-β-hydroxyaspartic acid and erythro-β-hydroxyasparagine as single enantiomers in a few steps.
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http://dx.doi.org/10.1021/acs.orglett.9b00664 | DOI Listing |
Chem Sci
December 2024
Department of Chemistry, Indian Institute of Science Education and Research (IISER) Bhopal Academic Building - 2, Bhopal By-pass Road, Bhauri Bhopal-462066 India
Herein, we unveiled a regio- and diastereoselective synthesis of cyclobutylated phenothiazines, a unique class of structural congeners of phenothiazines visible-light-irradiated intermolecular [2 + 2]-cycloaddition reaction, from readily available naphthoquinones, 2-aminothiophenols, and styrenes, either in a two-step or three-component coupling process. By varying substitutions in all three coupling partners, a library of cyclobutylated phenothiazines, including late-stage derivatization with five commercial drugs, has been realized with up to 97% isolated yield. In contrast to the reported pathways, the developed [2 + 2]-photocycloaddition seems to proceed a 'photoinduced-electron-transfer' (PET) mechanism, which is well corroborated with the experimental observations, Rehm-Weller equation, and computation studies.
View Article and Find Full Text PDFJ Am Chem Soc
November 2024
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India.
The direct utilization of carbon dioxide as an ideal one-carbon source in value-added chemical synthesis has garnered significant attention from the standpoint of global sustainability. In this regard, the photo/electrochemical reduction of CO into useful fuels and chemical feedstocks could offer a great promise for the transition to a carbon-neutral economy. However, challenges in product selectivity continue to limit the practical application of these systems.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
December 2024
Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Binhai New City, 350207, Fuzhou, China.
We present herein a catalytic enantioconvergent diamination of racemic allylic alcohols with the construction of two C-N bonds and 1,3-nonadjacent stereocenters. This iridium/chiral phosphoric acid cooperative catalytic system operates through an atom-economical borrowing hydrogen amination/aza-Michael cascade, and converts readily available phenylenediamines and racemic allylic alcohols to 1,5-tetrahydrobenzodiazepines in high enantioselectivity. An intriguing solvent-dependent switch of diastereoselectivity was also observed.
View Article and Find Full Text PDFChembiochem
December 2024
State Key Laboratory of Bioreactor Engineering, Shanghai Collaborative Innovation Centre for Biomanufacturing, East China University of Science and Technology, Meilong Road 130, Shanghai, 200237, China.
L-Threonine aldolase (L-TA) is a pyridoxal phosphate-dependent enzyme that catalyzes the reversible condensation of glycine and aldehydes to form β-hydroxy-α-amino acids. The combination of directed evolution and efficient high-throughput screening methods is an effective strategy for enhancing the enzyme's catalytic performance. However, few feasible high-throughput methods exist for engineering the C-stereoselectivity of L-TAs.
View Article and Find Full Text PDFChem Commun (Camb)
September 2024
Key laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064, China.
Asymmetric synthesis of 3-(3-indolomethyl)oxindoles through the addition of indole-substituted enolized ketoesters to 3-bromo-3-substituted oxindoles has been achieved using a ,'-dioxide/Ho(III) complex. A number of 3-(3-indolomethyl)oxindoles, which may possess biological activity, were obtained in good yields with high diastereo- and enantioselectivities (up to 97% yield, >19 : 1 dr, 98% ee). Furthermore, time-dependent reversal of diastereoselectivity enabled access to optically active diastereomers.
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