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The state of the art and recent developments in application of nuclear magnetic resonance (NMR) for structure elucidation and identification of small organic molecules are discussed. The recently suggested new two-dimensional (2D)-NMR experiments combined with the advanced instrumentation allow structure elucidation of new organic compounds at a sample amount of less than 10 µg. A pure shift approach that provides 1 H-decoupled proton spectra drastically simplified 1 H and 2D NMR spectra interpretation. The structure elucidation of extremely hydrogen-deficient compounds was dramatically facilitated due to the methodology based on combination of new 2D-NMR experiments providing long-range heteronuclear correlations with computer-assisted structure elucidation (CASE). The capabilities of CASE systems are discussed. The role of NMR-spectrum prediction in structure verification and NMR approaches for qualitative mixture analysis are considered. [ABSTRACT FROM AUTHOR]

the proposed structure of arneroma B has been revised from a cyclopentadienone to a 2,4-disubstituted furan. The reassignment has been confirmed by total synthesis of the revised structure. [Display omitted] • Molecular formula reassigned by MS. • Structure reassignment by NMR. • Confirmed by synthesis. [ABSTRACT FROM AUTHOR]

Abstract: Revised regiochemistry for the heterocyclization of electrophilic alkenes with tetranitromethane (TNM) in the presence of triethylamine, providing rapid access to nitroisoxazoles, is reported. The formation of 5-nitroisoxazoles previously incorrectly assigned as 3-nitro regioisomers, has now been established unambiguously by X-ray crystallography. Empirical computations with ACD/CNMR Predictor, based both on hierarchical ordering of spherical environments (HOSE) and an algorithm of artificial neural networks (ANN), and also Density Functional Theory computations of the 13C NMR chemical shifts for the 3- versus 5-nitroisoxazoles are shown to consistently match the spectra of the experimentally observed 5-regioisomers. [Copyright &y& Elsevier]

Abstract: In this article we describe a fast and accurate method of 13C NMR chemical shift prediction. The high speed of chemical shift calculation described is achieved using a simple structure description scheme based on individual atoms rather than functional groups. The systematic choice of an appropriate encoding scheme and the usage of partial least squares regression on a large training set has resulted in a robust and fast algorithm. The approach provides accuracy comparable with other well known approaches but demonstrates accelerated calculation speeds of up to a thousand times faster. [Copyright &y& Elsevier]