(-)-Erycibelline, the dihydroxynortropane alkaloid isolated from Erycibe elliptilimba Merr. et Chun., was synthesized using a cyclic nitrone as advanced intermediate, wherein the key step was the SmI(2)-induced intramolecular reductive coupling of cyclic nitrone with aldehyde which resulted in good yield and stereoselectivity.
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http://dx.doi.org/10.1039/c1ob06244a | DOI Listing |
Molecules
December 2024
Department of Chemistry and Biochemistry, Augustana University, Sioux Falls, SD 57197, USA.
This study examined the chemoselectivity and diastereoselectivity of silyl nitronate alkenyn-nitroethers in Intramolecular Silyl Nitronate Cycloadditions (ISNCs) to produce isoxazole derivatives with interesting medicinal properties. These reactions resulted in the formation of either dihydrofuro[3,4-c]isoxazolines/isoxazolidines and/or alkynyl moieties attached to 2,5-dihydrofuryl carbonyls. This study also discerned the diastereoselectivities of the resulting cyclic adducts and compared them to previous findings.
View Article and Find Full Text PDFRSC Adv
November 2024
Department of Chemistry, Faculty of Science, Masaryk University Kotlářská 2 CZ 611 37 Brno Czech Republic
We report the design, synthesis, electrochemical, UV-vis, fluorescence, and computational study of nine π-linked donor-acceptor (D-π-A) chromophores. The series of novel compounds comprises a terphenyl, terthiophene, or 2,5-diphenyl thiophene linker, with one electron-donating group (methyl or ,-diethyl) and one electron-withdrawing group (nitrone, formyl, or dicyanovinyl) at opposite ends of the molecule. The HOMO-LUMO gaps were determined cyclic voltammetry and found to correspond well to DFT-calculated values.
View Article and Find Full Text PDFNitrones are widely used as 1,3-dipoles in organic synthesis, but control of their reactions is not always easy. This review outlines our efforts to make the reactions of nitrones more predictable and easier to use. These efforts can be categorized into (1) 1,3-nucleophilic addition reaction of ketene silyl acetals to nitrones, (2) geometry-controlled cycloaddition of C-alkoxycarbonyl nitrones, (3) stereo-controlled cycloaddition using double asymmetric induction, and (4) generation of nitrones by N-selective modification of oximes.
View Article and Find Full Text PDFOrg Biomol Chem
August 2024
Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad de Salamanca. Plaza de los Caídos 1-5, 37008 Salamanca, Spain.
This communication describes a solution to the vexing problem of synthesis of 4-nitroisoxazolidine rings from cyclic nitrones and β-nitrostyrenes. The adduct 2 is quantitatively synthesised from -β-nitrostyrene under mild conditions avoiding purification, while the adduct 4 is obtained at higher temperatures. Furthermore, a Crystallization-Induced Diastereomer Transformation (CIDT) process was used to epimerise the NO bond from 2 to the adduct 3 with total conversion assisted by the -halogen substitution of the aromatic ring without any additives.
View Article and Find Full Text PDFEur J Med Chem
September 2024
Beijing National Laboratory for Molecular Science (BNLMS), CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China; University of Chinese Academy of Sciences, Beijing, 100049, China. Electronic address:
Broussonetine S (9), its C-1' and C-10' stereoisomers, and their corresponding enantiomers have been synthesized from enantiomeric arabinose-derived cyclic nitrones, with cross metathesis (CM), epoxidation and Keck asymmetric allylation as key steps. Glycosidase inhibition assays showed that broussonetine S (9) and its C-10' epimer (10'-epi-9) were nanomolar inhibitors of bovine liver β-galactosidase and β-glucosidase; while their C-1' stereoisomers were 10-fold less potent towards these enzymes. The glycosidase inhibition results and molecular docking calculations revealed the importance of the configurations of pyrrolidine core and C-1' hydroxyl for inhibition potency and spectra.
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