Structure elucidation, computer-assisted

The goal of computer-assisted stmcture elucidation (CASE) is the derivation of all possible structures that are consistent with a set of spectroscopic data, with the minimum of intervention by the spectroscopist. If computer-assisted 

In recent decades, much attention has been paid to the application of artificial neural networks as a tool for spectral interpretation (see, e.g.. Refs. [104, 105]). The ANN approach app]ied to vibrational spectra allows the determination of adequate functional groups that can exist in the sample, as well as the complete interpretation of spectra. Elyashberg [106] reported an overall prediction accuracy using ANN of about 80 % that was achieved for general-purpose approaches. Klawun and Wilkins managed to increase this value to about 95% [107]. 

Neural networks have been applied to IR spectrum interpreting systems in many variations and applications. Anand [108] introduced a neural network approach to analyze the presence of amino acids in protein molecules with a reliability of nearly 90%. Robb and Munk [109] used a linear neural network model for interpreting IR spectra for routine analysis purposes, with a similar performance. Ehrentreich et al. [110] used a counterpropagation network based on a strategy of Novic and Zupan [111] to model the correlation of structures and IR spectra. Penchev and co-workers [112] compared three types of spectral features derived from IR peak tables for their ability to be used in automatic classification of IR spectra. 

In many cases, structure elucidation with artificial neural networks is limited to backpropagation networks [113] and, is therefore performed in a supervised man- 

Schaefer III, P. R. Schreiner (Eds.), John Wiley Sons, Chichester, 1998, pp. 1845-1857. pq ACD/lLab - Interactive Laboratory, http //wwiv.acdlab5.com/ilab p7] Chemical Concepts (Whey-VCH), http //www.chemicalconcepts.com p ] Bio-Rad Laboratories, Inc., kttp //wmv.bio-rad.com P9] M. Tusar, L. Tusar, S. Bohanec, 

Molecular Spectral Analysis and Computers, Nauka, Moskau, 1980 (in Russian). 

---

P7] N.A. B. Gray, Computer-Assisted Structure Elucidation, Wiley, New York, 1986. 

However, better use of spectral information for more rapid elucidation of the structure of a reaction product, or of a natural product that has just been isolated, requires the use of computer-assisted structure elucidation (CASE) systems. The CASE systems that exist now are far away from being routinely used by the bench chemist. More work has to go into their development. 

Warr WA (1993) Computer-assisted structure elucidation. Anal Chem 65 1045A 1087A... 

CASE (computer-assisted structure elucidation) programs. ... 

Christie, B. D. Munk, M. E. "Computer-assisted Structure Elucidation Using 2-Dimensional NMR Data", 190th ACS National Meeting, Chicago, IL (1985). 

D. H. Smith, ed., Computer-Assisted Structure Elucidation, ACS Symposium Series, American Chemical Society, Washington DC, 1977. 

Diallo, M. S., Simpson, A., Gassman, R, Faulon, J. L., Johnson, J. H., Jr., Godard, W. A., Ill, and Hatcher, P. G. (2003). 3-D structural modeling of humic acids through experimental characterization, computer assisted structure elucidation and atomic simulations. I. Chelsea soil humic acid. Environ. Sci. Technol. 37,1783-1793. 

Gray, N.A.B. (1986). Computer-assisted structure elucidation, Wiley, New York and London. 

A 2004 review outlines the developments in computer-assisted structure elucidation (CASE) between 1999 and 2004.114 Elyashberg et al. have recently reviewed the current state-of-the-art in the field of CASE and structure... 

Diallo M.S. et al., Molecular modeling of Chelsea humic acid A hierarchical approach based on experimental characterization, computer-assisted structure elucidation, and atomistic simulations,Abstr. Pap. Am. Chem. Soc., 219,115-ENVR., 2000. 

Computer-assisted Structure Elucidation (CASE) Applications Employing Chemical Shift Correlation Data... 

There have been very few reports of the combined use of computer-assisted structure elucidation methods that have employed any form of data, whether direct or long-range correlation. Two papers appeared in 1999, the first by Kock, Junker, and Lindel [43]. These authors compared the application of computer-assisted structure elucidation methods to the alkaloid oroidin (3) with and without the inclusion of chemical shift correlation data. The tabulated results obtained for oroidin and reported in the study are quite interesting in terms of the impact of the availability of chemical shift correlation data. 

Much of the research and development on computer-assisted structure elucidation (CASE) has been reported in recent decades. The key problem with CASE is that the system should integrate different pieces of information from multiple spectra (such as one- and two-dimensional H, C NMR spectra, IR spectra, and mass spectroscopy spectra), filter redundant information, generate a reasonable number of structural candidates, verify the candidates, and eventually suggest the best structure(s) for the chemist. 

---