Fast determination of 13C NMR chemical shifts using artificial neural networks

Nine different artificial neural networks were trained with the spherically encoded chemical environments of more than 500 000 carbon atoms to predict their C-13 NMR chemical shifts. Based on these results the: PC-program "C_shift" was developed which allows the calculation:of the C-13 NMR spectra of any proposed molecular structure consisting of the covalently bonded elements C, H, N, O, P, S and the halogens. Results were obtained with a mean deviation as low as 1.8 ppm; this accuracy is equivalent to a determination on the basis of a large database but, in a time as short as known from increment calculations, was demonstrated exemplary using the natural agent epothilone A. The artificial neural networks allow simultaneously a precise and fast prediction of a large number of C-13 NMR spectra, needed for high throughout NMR and screening of a substance or spectra libraries.