COMPUTER-ASSISTED STRUCTURE GENERATION FROM A GROSS FORMULA .6. REDUCING THE STRUCTURAL REDUNDANCY BY THE EMPLOYMENT OF 2D NMR SPECTRAL INFORMATION

The use of C-13 chemical shift/structure relationships and 2D NMR information from different techniques as a constraint for the structure generation is discussed, and the development of a hierarchical multilevel generation procedure is made, the input information being molecular empirical formula and C-13 and H-1 spectra with their cross peak assignments from the 2D maps. These form the basis for a heuristic search procedure over the generation tree. This search implies that at each level of the structure formation all possible extensions are investigated and only those with the best fit to the available spectral information are taken onto the next level of structure construction. Since the spectral information is uncertain in its nature, some elements of fuzzy logic are used in the determination of the hybridization states of the carbon atoms arbitrarily assigned with C-13 NMR signals, and in the breadth-first-check procedure for selection of the proper extensions.