Applications of artificial intelligence to structure determination of organic compounds. XX^*. Determination of groups attached to the skeleton of natural products using ¹³C nuclear magnetic resonance spectroscopy

Abstract

A procedure for the identification of substituent groups (viz. angelate, tiglate, etc.) attached to any of the atoms in the conventional skeleton of a natural product is described. It consists in the use of the program MACRONO, which was developed for finding subspectra due to the carbons in the said substituent groups amid the raw13C NMR spectroscopic data from any given natural product (by means of comparisons of all possible subsets of the observed chemical shifts with those contained in an apposite database, built with literature13C NMR spectroscopic data regarding those groups). This procedure enables one to expunge the chemical shifts not due to skeletal carbons from the initial dataset, which then can be input to the expert system SISTEMAT, for skeletal identification.

Prediction of substituent types and positions on skeleton of eudesmane-type sesquiterpenes using generalized regression neural network (GRNN)

“…The structure of any natural product is conventionally divisible into three sub-units: (i) the skeletal atoms; (ii) heteroatoms directly bonded to the skeletal atoms or unsaturations between them; and (iii) secondary carbon chains, usually bound to a skeletal atom through an ester or ether linkage (Rodrigues et al, 1997). For identification purposes and for structural elucidation of new compounds, it is necessary to have access to extensive list of their structural data.…”

REGRAS: an auxiliary program for pattern recognition and substructure elucidation of monoterpenes

“…3, the REGRAS program makes the disfunctionalization of the substance spectrum. The data of 13 C NMR referring to the present substituents were previously identified and removed through the MACRONO program [19,20]. At this point of analysis, the program shows, for the monoterpene in Fig.…”

Prediction of Substituent Types and Positions on Skeleton of Myrcane-type Monoterpenoids using Generalized Regression Neural Network

“…The structure of any natural product is conventionally divisible into three sub-units: (i) the skeletal atoms; (ii) heteroatoms directly bonded to the skeletal atoms or unsaturations between them; and (iii) secondary carbon chains, usually bound to a skeletal atom through an ester or ether linkage [6]. A procedure that utilizes 13 C NMR for terpenoid skeleton identification has been described previously.…”

“…Another program, MACRONO (also written for SISTEMAT) could expunge chemical shifts not due to the skeletal carbons from the initial dataset, which can then be input into SISTEMAT for skeletal identification. A new version of the program was successfully tested in the identification of the substituents and skeletons of 60 compounds [6,9]. SISTEMAT has been found to achieve both high reliability and good performance when applied to structural elucidations and chemical shift evaluations of monoterpenoids.…”