Theoretical insight into the on-water catalytic effect in the biogenesis of triterpene dimers: from one-step to two-step hetero Diels–Alder reactions

Autor:	Carolina S. Castro-Segura, Mariana Quesadas-Rojas, Gonzalo J. Mena-Rejón, David Cáceres-Castillo, Ramiro F. Quijano-Quiñones
Rok vydání:	2021
Předmět:	ONIOM chemistry.chemical_classification Dimer One-Step General Chemistry Catalysis chemistry.chemical_compound Nucleophile chemistry Triterpene Computational chemistry Materials Chemistry Michael reaction Molecule Biogenesis
Zdroj:	New Journal of Chemistry. 45:22417-22423
ISSN:	1369-9261 1144-0546
Popis:	The reaction for the formation of the xuxuarine Aα triterpene dimer in an aqueous medium was studied using the ONIOM/CPCM-X scheme at the ONIOM(M06-2X/6-31G(d,p):PM6) level of theory, along with the inclusion of one and two explicit water molecules. The results show that the geometry of the water molecules in the complex of reactants switches the mechanism from a one-step to a two-step hetero Diels–Alder (HDA) reaction. The reaction begins with a Michael addition assisted by water, which is the rate-limiting step. Then, nucleophilic addition–protonation involving nucleophilic attack at the positive carbon center of the carbonyl group takes place. The two-step mechanism has an activation free energy that is 4.7 kcal mol−1 lower than the one-step mechanism, providing evidence of an alternative two-step water-assisted reaction for the biogenic origin of triterpene dimers.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::7c941bf08f19beccd78fb5c838a90de3 https://doi.org/10.1039/d1nj04221a Zobrazit plný text záznamu