Highly diastereoselective epoxidations of allyl-substituted cycloalkenes including allylic alcohols, esters, and amines using sterically bulky metalloporphyrins [Mn(TDCPP)Cl] (1) and [Ru(TDCPP)CO] (2) as catalysts have been achieved. The "1 + H(2)O(2)" and "2 + 2,6-Cl(2)pyNO" protocols afforded trans-epoxides selectively in good yields (up to 99%) with up to >99:1 trans-selectivity.
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http://dx.doi.org/10.1021/ol0496475 | DOI Listing |
J Org Chem
January 2025
Centro de Investigaciones Químicas-IICBA, Universidad Autónoma del Estado de Morelos. Av. Universidad 1001, 62209 Cuernavaca, Morelos, Mexico.
Phosphonic analogs of octahydroisoindole-1-carboxylic acids are bicyclic proline derivatives of interest in drug design and enzymatic mechanism studies. Here we report the stereoselective synthesis of the - and -fused octahydroisoindole system using oxazoloisoindolone lactam and 1,2-cyclohexanedicarboxylic anhydride as advanced chiral precursors, respectively, yielding enantiopure octahydroisoindolone intermediates with the desired stereochemistry at the ring junction. Finally, using these intermediates, the target (1,3a,7a)- and (1,3a,7a)-octahydroisoindole-1-phosphonic acids and their enantiomers were obtained with complete stereocontrol via highly diastereoselective addition of trimethyl phosphite to chiral -acyliminium ions as the key step.
View Article and Find Full Text PDFJ Org Chem
January 2025
Department of Chemistry, New York University, 100 Washington Square East, New York, New York 10003, United States.
Nucleophilic substitution reactions of C-2-acyloxy furanosyl acetals can be highly diastereoselective. We here show that the presence of a less electron-donating -nitrobenzoyloxy group at C-2 of a furanosyl acetal can be of use to control the 1,2- stereoselectivity of acetal substitution reactions with higher stereoselectivity than the analogue with the more electron-donating benzoyloxy group, just as what was observed in the pyranosyl system. Computational results support a reaction manifold involving both open oxocarbenium ions and -dioxolenium ions to provide the 1,2- and 1,2- products.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
January 2025
Shanghai Institute of Materia Medica Chinese Academy of Sciences, Chemical Biology Research Center, 201203, Shanghai, CHINA.
Aldolases are powerful C-C bond-forming enzymes for asymmetric organic synthesis because of their supreme stereoselectivity, diverse electrophiles and nucleophiles, and promising scalability. Stereodivergent engineering of aldolases to tune the selectivity for the synthesis of stereoisomers of chiral molecules is highly desirable but has rarely been reported. This study documented the semirational engineering of the decarboxylative aldolase UstD with the focused rational iterative site-specific mutagenesis (FRISM) strategy to perform a C-C bond-forming reaction with dione electrophiles.
View Article and Find Full Text PDFJ Am Chem Soc
January 2025
Institute of Organic Chemistry, University of Leipzig, 04103 Leipzig, Germany.
The enantioselective synthesis of 1,4-dicarbonyl compounds continues to pose a significant challenge in organic synthesis, and a catalytic process which generates two adjacent stereogenic centers with full stereochemical control is lacking until now. The 1,4-relationship of the functional groups requires an Umpolung strategy as one of the α-carbonyl positions has to be inverted into an electrophilic center to react with a normal enolate. We report herein the highly enantio- and diastereoselective addition of silyl ketene acetals toward electrophilic 1-azaallyl cations to furnish chiral 4-hydrazonoesters, which are masked 1,4-dicarbonyl compounds.
View Article and Find Full Text PDFJ Am Chem Soc
January 2025
Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.
A concise and convergent synthesis of the isosteroidal alkaloids veratramine and 20--veratramine has been accomplished. A Horner-Wadsworth-Emmons olefination joins two chiral building blocks of approximately equal complexity and a transition-metal catalyzed intramolecular Diels-Alder cycloaddition-aromatization cascade constructs the tetrasubstituted arene. Other key steps include a highly diastereoselective crotylation of an -sulfonyl iminium ion and an Eschenmoser fragmentation.
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