Magnetic Resonance in Chemistry

A parallel localized spectroscopy (PALSY) method is presented to speed up the acquisition of multidimensional NMR spectra. The sample is virtually divided into a discrete number of nonoverlapping slices that relaxes independently during consecutive scans of the experiment. PALSY does not impose any limit in the achievable resolution in any dimension, uses conventional processing and once it is calibrated can be used routinely. The method was tested to acquire in parallel 2D COSY, 2D DQF-COSY and 2D TQF-COSY.

QUANTAS is a software-based procedure for automatic external standard quantification by NMR. It compensates for various experimental parameters and is applicable to all nuclei and modern spectrometers.

Inductively coupled microcoils for NMR spectroscopy and imaging experiments using a commercial liquids NMR probe are examined. These coils can be employed without any modifications to existing NMR hardware. Sensitivity enhancements of an order of magnitude are achievable for spectroscopy and imaging experiments of chemical and biological samples with sample sizes < 1.0 mg.

A method is presented that allows for retrieving 1D spectra of individual components of a mixture from rapidly and sparsely acquired 2D-TOCSY experiment. This decomposition is achieved using non-negative matrix factorization, also referred to as multivariate curve resolution.

NMR analysis of complex mixtures can be significantly simplified using polyethyleneglycol (PEG) as resolving additive in DOSY NMR technique, which allows the extraction of individual spectra of mixture components with differing polarity.

Subtle NMR receiver gain compression is associated with reduced resonance integration and narrower line width at low (2% or lower) peak height.

¹¹⁹Sn relay allows ¹H,⁵⁷Fe correlation spectra in 18 min in the absence of direct ¹H⁵⁷Fe scalar coupling. C₆D₆ (0.08 M solution of Cp(dppm)FeSnMe₃.

We demonstrate the utility of a methodology based on the estimation of root-mean-square-deviation between two sets of chemical shifts to rapidly assign the 3D-spectra of a metal binding protein in its holo-state from the knowledge of its assignments in apo-state, the spectra of a protein in its paramagnetic state from the knowledge of its assignments in diamagnetic state and finally, the spectra of a mutant protein from the knowledge of the chemical shifts of the corresponding wild-type protein.

Some efficient schemes for heteronuclear dipolar decoupling in liquid crystal NMR are formulated by supercycling SWf-TPPM, a sequence introduced recently for this purpose in rotating solids. These sequences are compared with the other commonly used decoupling schemes in liquid crystals. The effectiveness of the decoupling programmes with respect to experimental parameters such as RF field strength, decoupler offset frequency and phase angle is also presented.

The synthesis of 1- and 2- benzoyloxycinnamoyal naphthones was achieved in one step using hydroxyl napthones and substituted cinnamic acids in the presence of catalytic amount of phosphorus oxychloride. Structural characterization was accomplished using high resolution NMR spectroscopy. Chemical shifts of the compounds were compared and the change in the chemical shifts relative to electron donating and withdrawing groups is presented.

The structure of the reactive intermediate, which was difficult to be detected because of the short life time in the reaction mixture, was elucidated as a 2-methyl-4-methyleneoxazol-5(4H)-one (A) by using a 2D-NMR technique, diffusion-ordered spectroscopy (DOSY).

The application of the QDEPT and QHSQC principles for long-range interactions for the direct detection of non-proton-bearing ¹⁵N is proffered as a general solution together with multiselective PT and triple INEPT for overcoming convoluted responses.

Besides three known biphenyldibenzodioxinbisbenzylisoquinoline alkaloids, two novel alkaloids of the same group have been isolated from the fruits of Tiliacora racemosa. The structure of these new compounds designated tiliaimine and nordinklacorine were established on the basis of 1D and 2D NMR spectroscopy, including COSY, TOCSY, ROESY, HMBC and HSQC experiments.

Three new acacic acid derivatives, named coriariosides C, D and E (1–3) were isolated from the roots of Albizia coriaria. Their structures were elucidated on the basis of extensive 1D-and 2D-NMR studies and mass spectrometry.