Subject(s)
HIV Infections/nursing , Nursing , Stereotyping , Attitude of Health Personnel , HIV Infections/psychology , HumansABSTRACT
Aryl imidazolylsulfonates participate as electrophilic coupling partners in palladium-mediated cross-coupling reactions. The aryl imidazolylsulfonates display good stability while maintaining good reactivity in a variety of palladium-catalyzed coupling reactions. Imidazolylsulfonates are a practical and economic alternative to triflates.
Subject(s)
Arylsulfonates/chemistry , Combinatorial Chemistry Techniques , Imidazoles/chemistry , Palladium/chemistry , Catalysis , Mesylates/chemistry , Molecular StructureABSTRACT
GHSQC-TOCSY experiments allow sorting of proton-proton connectivity information as a function of (13)C chemical shift. GHSQC-TOCSY is a relatively insensitive 2D NMR experiment. Given two coherence transfer experiments, A --> B and A --> C, it is possible to indirectly determine B <--> C. Unsymmetrical indirect covariance processing of a (1)H- (13)C GHSQC and a GCOSY spectrum afforded a GHSQC-COSY spectrum, with an information content analogous to a GHSQC-TOCSY experiment. However, GHSQC-TOCSY is of significantly lower sensitivity and the data require considerably more time to acquire than either of the component experiments. Investigators needing access to GHSQC-TOCSY type data can, in principle, access it from more readily acquired 2D NMR data. Strychnine ( 1) was used as a model compound to illustrate this capability.
Subject(s)
Magnetic Resonance Spectroscopy , Models, Chemical , Strychnine/chemistry , Carbon Isotopes , Molecular StructureABSTRACT
Utilization of long-range (1)H--(15)N heteronuclear chemical shift correlation has continually grown in importance since the first applications were reported in 1995. More recently, indirect covariance NMR methods have been introduced followed by the development of unsymmetrical indirect covariance processing methods. The latter technique has been shown to allow the calculation of hyphenated 2D NMR data matrices from more readily acquired nonhyphenated 2D NMR spectra. We recently reported the use of unsymmetrical indirect covariance processing to combine (1)H--(13)C GHSQC and (1)H--(15)N GHMBC long-range spectra to yield a (13)C--(15)N HSQC-HMBC chemical shift correlation spectrum that could not be acquired in a reasonable period of time without resorting to (15)N-labeled molecules. We now report the unsymmetrical indirect covariance processing of (1)H--(13)C GHMBC and (1)H--(15)N IMPEACH spectra to afford a (13)C--(15)N HMBC-IMPEACH spectrum that has the potential to span as many as six to eight bonds. Correlations for carbon resonances long-range coupled to a protonated carbon in the (1)H--(13)C HMBC spectrum are transferred via the long-range (1)H--(15)N coupling pathway in the (1)H--(15)N IMPEACH spectrum to afford a much broader range of correlation possibilities in the (13)C--(15)N HMBC-IMPEACH correlation spectrum. The indole alkaloid vincamine is used as a model compound to illustrate the application of the method.
Subject(s)
Magnetic Resonance Spectroscopy/methods , Software , Carbon Isotopes , Molecular Structure , Nitrogen Isotopes , StereoisomerismABSTRACT
There has been considerable interest over the past decade in the utilization of direct and long-range 1H- 15N heteronuclear shift correlation methods at natural abundance to facilitate the elucidation of small molecule structures. Recently, there has also been a high level of interest in the exploration of indirect covariance NMR methods. Our initial explorations in this area led to the development of unsymmetrical indirect covariance methods, which allow the calculation of hyphenated 2D NMR spectra such as 2D GHSQC-COSY and GHSQC-NOESY from the discrete component 2D NMR experiments. We now wish to report the utilization of unsymmetrical indirect covariance NMR methods for the combination of 1H- 13C GHSQC and 1H- 15N long-range (GHMBC, IMPEACH-MBC, CIGAR-HMBC, etc.) heteronuclear chemical shift correlation spectra to determine 15N- 13C correlation pathways.
Subject(s)
Electronic Data Processing/methods , Magnetic Resonance Spectroscopy/methods , Organic Chemicals/chemistry , Carbon Isotopes , Molecular Structure , Nitrogen IsotopesABSTRACT
We have recently demonstrated that unsymmetrical indirect covariance NMR methods can be used to mathematically calculate the equivalent of low sensitivity, hyphenated NMR experiments by combining data from a pair of higher sensitivity experiments. The present report demonstrates the application of this method to the combination of HSQC and NOESY spectra to provide results comparable to HSQC-NOESY data, albeit with greater sensitivity and with considerably less spectrometer time.
