Structure elucidation methodology for disaccharides based on carbon-13 nuclear magnetic resonance spectrum simulation

Abstract

Molecular mechanics techniques are used to derive structural parameters that allow carbon-13 nuclear magnetic resonance spectra of disaccharides to be modeled. On the basis of a collection of 40 disaccharide spectra, four linear models are derived that allow complete spectra to be simulated. On the basis of these 40 compounds, the average difference between simulated and observed chemical shifts is +/- 0.45 ppm. The majority of structural parameters used are based on interatomic distances computed from modeled three-dimensional atomic coordinates. Found particularly useful in modeling the disaccharide spectra are the effects of oxygen electron lone pairs and encodings of the structural environments of hydrogens alpha to the carbon whose chemical shift is being predicted. The computed models are examined, and their predictive ability is assessed. The potential application of the methodology to the structure elucidation of disaccharides is demonstrated.

NMR Chemical Shift Predictions and Structural Elucidation of Oligo- and Polysaccharides by the Computer Program CASPER

“…[9][10][11] Computerized methods based on NMR chemical shift data emerged in the 1980s, in particular using 13 C chemical shifts and were based on increment rules, in which corrections (positive or negative) are added to the base value of an atom in a structure as a result of a substituent and/or steric interactions, if present. 12 In the carbohydrate field these developments include CASPER, 13 an acronym for Computer Assister SPectrum Evaluation of Regular polysaccharides, a 13 C NMR approach to the structural analysis of carbohydrates, 14 a carbon-13 NMR methodology for their structural elucidation 15,16 as well as utilization of 13 C NMR for identification of mannooligosaccharides and glycopeptides. 17 CASPER was subsequently enhanced to also include 1 H NMR data, 18,19 2D NMR representations of spectra 18 and to address oligosaccharide structures.…”

Evaluation of automated methods for the selection of models for simulation of carbon-13 nuclear magnetic resonance spectra of keto steroids

“…Work in this laboratory led to the development of a computer-based system for simulation 0003-2700/91 /0363-0443$02.50/0 of 13C NMR spectra (5,6) and its subsequent application to several different types of molecules: cycloalkanes (5), cyclohexanols and decalols (7), hydroxy steroids (8), cyclopentanes and cyclopentanols (9), norboranols (10), cyclohexanones and decalones (11), piperidines (12), polychlorinated biphenyls (13,14), and aromatic molecules (15). Related work by Small and co-workers has focused on spectral simulations for mono-and disaccharides (16,17) and linear aromatic compounds (18). The long-term goal of this research is to develop an interactive software system for use in simulating 13C NMR spectra for a wide assortment of chemical compounds.…”