TY - JOUR
T1 - Nuclear magnetic resonance assignment strategy for pentacyclic triterpenes, using lup-20(29)-ene from Pilotrichella flexilis as model system, combining spectrally filtered proton-to-carbon schemes and DFT–GIAO approach
AU - Herbert-Pucheta, Jose Enrique
AU - Mejía-Lara, Cinthia
AU - Reyes-Trejo, Benito
AU - Reyes, Lino
AU - Zuleta-Prada, Holber
N1 - Publisher Copyright:
© 2019, The Author(s).
PY - 2019/12/1
Y1 - 2019/12/1
N2 - The present work comprises a method to obtain full proton-to-carbon nuclear magnetic resonance chemical shift assignment of a C30H50 lup-20(29)-ene, for the first time obtained from the Mexican native mosses Pilotrichella flexilis, wherein said method consists in a combination of the following NMR schemes: 1D-13C (DEPT-135), 2D-{1H–13C} HMBC with a spectral filter for promoting only weak-c.a. 2 Hz-long-range scalar couplings, 2D-{1H–1H} EXSY with long mixing times to favour only weak H–H dipolar correlations and ultra-high resolution one- and two-dimensional 1H instant homodecoupling Psyche pure shift. Full set of assigned resonances were compared against the theoretical isotropic chemical shifts computed with a gauge invariant atomic orbital–density functional theory with self consistent reaction field calculation, retrieving accurate agreements, despite the intrinsic severe signal overlap that these C30 hydrocarbon triterpenes experimentally present. Therefore, a 3D-structure supported by experimental NMR data of this type of important metabolite precursor in plants can be proposed.
AB - The present work comprises a method to obtain full proton-to-carbon nuclear magnetic resonance chemical shift assignment of a C30H50 lup-20(29)-ene, for the first time obtained from the Mexican native mosses Pilotrichella flexilis, wherein said method consists in a combination of the following NMR schemes: 1D-13C (DEPT-135), 2D-{1H–13C} HMBC with a spectral filter for promoting only weak-c.a. 2 Hz-long-range scalar couplings, 2D-{1H–1H} EXSY with long mixing times to favour only weak H–H dipolar correlations and ultra-high resolution one- and two-dimensional 1H instant homodecoupling Psyche pure shift. Full set of assigned resonances were compared against the theoretical isotropic chemical shifts computed with a gauge invariant atomic orbital–density functional theory with self consistent reaction field calculation, retrieving accurate agreements, despite the intrinsic severe signal overlap that these C30 hydrocarbon triterpenes experimentally present. Therefore, a 3D-structure supported by experimental NMR data of this type of important metabolite precursor in plants can be proposed.
KW - Homonuclear proton long-range through-space EXSY
KW - Lupene
KW - NMR spectroscopy
KW - Pentacyclic triterpenes
KW - Pureshift NMR
KW - Weak long-range heteronuclear through-bound HMBC
UR - http://www.scopus.com/inward/record.url?scp=85065651610&partnerID=8YFLogxK
U2 - 10.1186/s13765-019-0435-3
DO - 10.1186/s13765-019-0435-3
M3 - Artículo
AN - SCOPUS:85065651610
SN - 2468-0834
VL - 62
JO - Applied Biological Chemistry
JF - Applied Biological Chemistry
IS - 1
M1 - 28
ER -