title: (1)H chemical shift differences of Prelog-Djerassi lactone derivatives: DFT and NMR conformational studies.
abstract: This work reports an experimental and theoretical study of the conformational preferences of several Prelog-Djerassi lactone derivatives, to elucidate the (1)H NMR chemical shift differences in the lactonic core that are associated with the relative stereochemistry of these derivatives. The boat-like conformation of explains the anomalous (1)H chemical shift between H-5a and H-5b, in which the two methyl groups (C-8 and C-9) face H-5b, leading to its higher shielding effect.
authors.affiliation: Laboratório de Química Bio-orgânica e Laboratório de Cristalografia, Estereodinâmica e Modelagem Molecular, Universidade Federal de São Carlos, C.P. 676, São Carlos, Brazil. marcoantbf@gmail.com.
authors.forename: Túlio J
authors.initials: TJ
authors.lastname: Aímola
authors.forename: Dimas J P
authors.initials: DJ
authors.lastname: Lima
authors.forename: Luiz C
authors.initials: LC
authors.lastname: Dias
authors.forename: Cláudio F
authors.initials: CF
authors.lastname: Tormena
authors.forename: Marco A B
authors.initials: MA
authors.lastname: Ferreira
mesh_terms: D007783:Lactones / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D011522:Protons; D011789:Quantum Theory; D013237:Stereoisomerism
chemical_list: D007783:Lactones; D011522:Protons