INFERCNMR: A ¹³C NMR Interpretive Library Search System

Abstract

INFERCNMR is an automated (13)C NMR spectrum interpretation aid for use either as a stand-alone program or as a component of a comprehensive, computer-based system for the characterization of chemical structure. The program is an interpretive library search which requires a database of assigned (13)C NMR spectra. An interpretive library search does not require overall structural similarity between an unknown and a library entry in order to retrieve a substructure common to both. Input consists of the chemical shift and one-bond proton-carbon multiplicity of each signal in the spectrum, and the molecular formula of the unknown. Program output is one or more substructures predicted to be present in the unknown, each of which is assigned an estimated prediction accuracy.

1H and 13C NMR Analysis of the neo-Clerodane Diterpenoid Scutecyprin

“…General: 1 H, 13 C and 2D NMR spectra of 1 were recorded on a Bruker Avance II+ 600MHz NMR spectrometer operating at 600.130 MHz ( 1 H) and 150.903 MHz ( 13 C), using TMS as internal standard and CDCl 3 as solvent. The temperature was kept at 293.0 K for all NMR experiments.…”

“…As mentioned above, the carbon signal of C-14 is close to those of C-7 and C-12, but in the HSQC spectrum the cross peaks of the methylene protons at C-14 are distinguishable from those of the C-7 and C-12 methylene groups. The COSY and HMBC correlations of  H 1.68 listed in Table 1 prove that it is for one of the C-14 protons; the same refers to The 13 C NMR spectrum of scutecyprin was searched in a database of nearly 39,000 fully-assigned 13 C NMR spectra. The search method, the so called interpretive library search [13], retrieves substructures common to both the unknown and reference compounds and estimates the probability of substructure-presence by comprehensive statistics.…”

Interpretive Library Search of Plant Compound Spectra in a 13C NMR Database#

“…Computer searching in spectral libraries of fully-assigned 13 C NMR spectra of substructures or full structures is an essential part of structure elucidation and has been widely applied because this type of spectra reflects the nature of the skeletal backbone of an organic compound, information not as readily available by other spectroscopic techniques [1]. In this paper we describe an extensive test of a previously developed method for interpretive search in spectral libraries of fully-assigned 13 C NMR spectra [2]. The method is implemented into a Windows-based userfriendly program, called Infer C NMR.…”

“…Thus, if even only one of the retrieved substructures used as constraints is incorrect, every structure produced by structure generator will be invalid (the worst scenario) or no output structures will be generated because the constraints contradict each other or other spectral data (a better scenario). That is why the output from the interpretive 13 C NMR library search must have two very important features: high information content and high reliability.As described in a previous paper [2], the accuracy function was tested with a large validation set of nearly 12,740 spectra by leave-one-out cross-validation. These spectra were part of the library and some of them are not natural compounds but smaller ones produced by chemical synthesis.…”

“…As described in a previous paper [2], the accuracy function was tested with a large validation set of nearly 12,740 spectra by leave-one-out cross-validation. These spectra were part of the library and some of them are not natural compounds but smaller ones produced by chemical synthesis.…”