title: Biogenesis of Triterpene Dimers from Orthoquinones Related to Quinonemethides: Theoretical Study on the Reaction Mechanism.
abstract: The biogenetic origin of triterpene dimers from the Celastraceae family has been proposed as assisted hetero-Diels-Alder reaction (HDA). In this work, computational calculation of HDA between natural quinonemethides (tingenone and isopristimerol) and hypothetical orthoquinones has been performed at the M06-2X/6-31G(d) level of theory. We have located all the HDA transition states supporting the biogenetic route via HDA cycloadditions. We found that all reactions take place through a concerted inverse electron demand and asynchronous mechanism. The enzymatic assistance for dimer formation was analyzed in terms of the calculated transition state energy barrier.
authors.affiliation: Facultad de Química, Universidad Autónoma de Yucatán, Calle 43 No. 613, Col. Inalambrica, Mérida, Yucatán, C.P. 97069, Mexico. mariana_quesadas@yahoo.com.mx.
authors.forename: Mariana
authors.initials: M
authors.lastname: Quesadas-Rojas
authors.affiliation: Facultad de Química, Universidad Autónoma de Yucatán, Calle 43 No. 613, Col. Inalambrica, Mérida, Yucatán, C.P. 97069, Mexico. mrejon@uady.mx.
authors.forename: Gonzalo J
authors.initials: GJ
authors.lastname: Mena-Rejón
authors.affiliation: Facultad de Química, Universidad Autónoma de Yucatán, Calle 43 No. 613, Col. Inalambrica, Mérida, Yucatán, C.P. 97069, Mexico. david.caceres@correo.uady.mx.
authors.forename: David
authors.initials: D
authors.lastname: Cáceres-Castillo
authors.affiliation: Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Ciudad de México, C.P. 04510, Mexico. gecgb@unam.mx.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Cuevas
authors.affiliation: Facultad de Química, Universidad Autónoma de Yucatán, Calle 43 No. 613, Col. Inalambrica, Mérida, Yucatán, C.P. 97069, Mexico. ramiro.quijano@uady.mx.
authors.forename: Ramiro F
authors.initials: RF
authors.lastname: Quijano-Quiñones
mesh_terms: D053898:Biosynthetic Pathways; D061565:Cycloaddition Reaction; D008954:Models, Biological; D008956:Models, Chemical; D010944:Plants / Q000378:metabolism; D011789:Quantum Theory; D011809:Quinones / Q000378:metabolism*; D014315:Triterpenes / Q000378:metabolism*
chemical_list: D011809:Quinones; D014315:Triterpenes
keywords: Celastraceae; DFT; biogenesis; hetero Diels-Alder; quinonemethide