In the last decade, quantum chemical approaches have shown their potential in solving chemical problems. This has been mostly due to the ever increasing computational capabilities at a relatively affordable cost, and to a parallel development of user friendly software. While many aspects of molecular structure and dynamics may be solved with the use of classical methods based on empirical force fields, quantum chemistry allows the comprehension of many problems related to the electronic density distribution. In particular, quantum chemistry methods can be applied for calculating the spectroscopic properties of molecules, and the efficient prediction of UV, IR, CD, and NMR spectra have been extensively reported in the last fifteen years. NMR chemical shift calculation by quantum mechanical methods has attracted the interest not only of the theoretical chemists, but also of the experimental NMR spectroscopists. In fact, this kind of approach has been used by our and other research groups as a contribution to the structure elucidation of natural products. We have presented two original methodologies, based on GIAO (gauge including atomic orbitals) quantum-mechanical 13C chemical shift calculations, that have been efficiently employed as a support in the analysis of the NMR data of organic molecules. The first methodology regards the structure validation of natural products by means of GIAO 13C chemical shift calculations, while the second one, based on the same methodology, has been directed to the determination of the relative configuration of flexible compounds. For the interested readers, the most significant applications of quantum chemical calculations of NMR parameters in the resolution of stereochemical problems have been recently reported by us in two reviews. On the other hand, the scope of this chapter is to present a step-by-step guide for the chemical shift calculation of organic compounds in the determination of their relative configuration.

Quantum Chemical Calculation of Chemical Shifts in the Stereochemical Determination of Organic Compounds: A Practical Approach

DI MICCO, SIMONE;CHINI, MARIA GIOVANNA;RICCIO, Raffaele;BIFULCO, Giuseppe
2012

Abstract

In the last decade, quantum chemical approaches have shown their potential in solving chemical problems. This has been mostly due to the ever increasing computational capabilities at a relatively affordable cost, and to a parallel development of user friendly software. While many aspects of molecular structure and dynamics may be solved with the use of classical methods based on empirical force fields, quantum chemistry allows the comprehension of many problems related to the electronic density distribution. In particular, quantum chemistry methods can be applied for calculating the spectroscopic properties of molecules, and the efficient prediction of UV, IR, CD, and NMR spectra have been extensively reported in the last fifteen years. NMR chemical shift calculation by quantum mechanical methods has attracted the interest not only of the theoretical chemists, but also of the experimental NMR spectroscopists. In fact, this kind of approach has been used by our and other research groups as a contribution to the structure elucidation of natural products. We have presented two original methodologies, based on GIAO (gauge including atomic orbitals) quantum-mechanical 13C chemical shift calculations, that have been efficiently employed as a support in the analysis of the NMR data of organic molecules. The first methodology regards the structure validation of natural products by means of GIAO 13C chemical shift calculations, while the second one, based on the same methodology, has been directed to the determination of the relative configuration of flexible compounds. For the interested readers, the most significant applications of quantum chemical calculations of NMR parameters in the resolution of stereochemical problems have been recently reported by us in two reviews. On the other hand, the scope of this chapter is to present a step-by-step guide for the chemical shift calculation of organic compounds in the determination of their relative configuration.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11386/3345477
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