Homonuclear Hartmann-Hahn spectroscopy

Because of the complexity of the polyether antibiotics tittle progress has been made in stmcture determination by the chemical degradation route. X-ray methods were the techniques most successfully applied for the early stmcture elucidations. Monensin, X206, lasalocid, lysocellin, and salinomycin were included in nineteen distinct polyether x-ray analyses reported in 1983 (190). Use of mass spectrometry (191), and H (192) and nmr (141) are also reviewed. More recently, innovative developments in these latter techniques have resulted in increased applications for stmcture determinations. Eor example, heteronuclear multiple bond connectivity (hmbc) and homonuclear Hartmann-Hahn spectroscopy were used to solve the stmcture of portimicin (14) (193). East atom bombardment mass spectrometry was used in solving the stmctures of maduramicin alpha and co-factors (58). 

Homonuclear Hartmann-Hahn Spectroscopy or Total Correlation Spectroscopy 267... 

HOMONUCLEAR HARTMANN-HAHN SPECTROSCOPY (HOHAHA), OR TOTAL CORRELATION SPECTROSCOPY (TOCSY)... 

Homology modeling, 20 837 Homomenthyl salicylate, 22 16 physical properties of, 22 14t Homonuclear Hartmann-Hahn spectroscopy, 20 137 Homopolymerization, 10 183 of a-olelins, 16 110 ethene, 16 102-103 propene, 16 104-110 of VDC, 25 695-697 Homopolymers... 

Hartmann-Hahn-Hadamard spectroscopy Heteronuclear Hartmann-Hahn spectroscopy Heteronuclear-homonuclear Hartmann-Hahn spectroscopy... 

Heteronuclear multiple-quantum correlation Experiment for tailored correlation spectroscopy of H and H resonances in peptides and proteins Homonuclear Hartmann-Hahn spectroscopy Heteronuclear quadruple-quantum coherence Heteronuelear triple-quantum coherence Heteronuclear single-quantum coherence TOCSY sequences developed at the Indian Institute of Chemical Technology Insensitive nucleus enhancement by polarization transfer... 

An essentially identical experiment has also been referred to as Homonuclear Hartmann-Hahn spectroscopy [50,51] or HOHAHA (the two differ only in some technical details in the originally published sequences). This name arises from its similarity with methods used in solid-state NMR spectroscopy for the transfer of polarisation from proton to carbon nuclei (so-called crosspolarisation), which are based on the Hartmann-Hahn match described below. For the same reason, the transfer of magnetisation during the TOCSY sequence is sometimes referred to as homonuclear cross-polarisation. Throughout this text the original TOCSY terminology is used, although TOCSY and HOHAHA are now used synonymously in the chemical literature. 

HOHAHA Homonuclear Hartmann-Hahn spectroscopy (aka TOCSY) 5.7... 

Davis DG, Bax A (1985) Assignment of Complex H NMR Spectra via Two-Dimensional Homonuclear Hartmann-Hahn Spectroscopy. J Amer Chem Soc 107 2820... 

NMR is the tool most widely used to identify the structure of triterpenes. Different one-dimension and two-dimension techniques are usually used to study the structures of new compounds. Correlation via H-H coupling with square symmetry ( H- H COSY), homonuclear Hartmann-Hahn spectroscopy (HOHAHA), heteronuclear multiple quantum coherence (HMQC), heteronuclear multiple bond correlation (HMBC), distortionless enhancement by polarisation transfer (DEPT), incredible natural abundance double quantum transfer experiment (INADEQUATE) and nuclear Overhauser effect spectroscopy (NOESY) allow us to examine the proton and carbon chemical shift, carbon types, coupling constants, carbon-carbon and proton-carbon connectivities, and establish the relative stereochemistry of the chiral centres. 

Figure 5.48 The pulse sequence employed in 2D homonuclear Hartmann-Hahn spectroscopy. An extended MLEV-16 sequence is used. Trim pulses are applied before and after this pulse sequence in order to refocus the magnetization not parallel to the x-axis.

HOHAHA (Homonuclear Hartmann-Hahn Spectroscopy). This method is based on spin propagation (Braunschweiler and Ernst 1983 Summers et al. 

Davis DG, Bax A (1985a) Assignment of complex H NMR spectra via two-dimensional homonuclear Hartmann-Hahn spectroscopy. J Am Chem Soc 107 2820-2821 Davis DG, Bax A (1985b) Identification of H NMR spectra by selective excitation of experimental subspectra. J Am Chem Soc 107 7197-7198 De Bruyn A, Zhang W, Budesinsky M (1989) NMR Study of three heteroyohimbine derivatives from Rauwolfia serpentina stereochemical aspects of the two isomers of reserpiline hydrochloride. Magn Reson Chem 27 935-940... 

The most commonly used 2D nmr technique applied to through-bond interactions is termed (7 ) correlated spectroscopy (COSY), others are total correlation spectroscopy (TOCSY), which allows somewhat longer-range through-bond connectivities to be observed than with COSY, spin echo coherence transfer spectroscopy (SECSY), relayed coherence transfer spectroscopy (RELAY), double quantum spectroscopy (DQNMR) and homonuclear Hartmann-Hahn spectroscopy (HOHAHA). The most commonly used 2D nmr technique applied to through-space interactions is termed nuclear Overhauser effect spectroscopy (NOESY) also used is the closely related rotating-frame NOESY (ROE-SY). 

Reviews have appeared on the use of high resolution n.m.r. spectroscopy in the structural determination of complex carbohydrates and of some 3-0-, 4-0-, and 3,4-di-O-glycopyranosyl-substituted methyl D-gtycopyranosides. The latter publication includes complete assignments of and C-n.m.r. resonances as well as conformational studies using HSEA effect theory. The application of various njnj. techniques (multi-relayed correlation, H- H-correlated, triple quantum field H- H-correlated and H- H homonuclear Hartmann Hahn spectroscopy) to carbohydrate analysis has been reviewed in Japanese, and in a further Japanese review the interactions of metal ions with uronic acids and amino sugars as observed by the lanthanide-probe n.m.r. method are discussed/... 

HOHAHA HHPA Homonuclear Hartmann-Hahn Spectroscopy Higher Random Phase Approximation... 

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