INDOR spectroscopy

The first measurements of pH-dependences of13C spectra of amino acids were carried out by INDOR spectroscopy [96]. Pulse Fourier transform 13C NMR measurements are less... 

These two, distinct modes of INDOR spectroscopy will now be discussed, before an attempt is made to illustrate their practical outcome. 

It is appropriate to discuss here some specific examples of INDOR spectroscopy as it applies to carbohydrate systems. 

Early experiments in this area utilized B — B homonuclear CW INDOR spectroscopy (Chapter 2) at 80.2 MHz, applied to some derivatives of [B oHi4] and ortAo-[C2BjoHi2], " and to some somewhat more demanding 18-vertex species. The experiments were very successful for the compounds examined, but unfortunately the work has not since been extended further. However, apart from the assignments, a number of important features, such as an effective absence of coupling... 

INDOR spectroscopy has been used to reveal hidden chemical shifts... 

Table II presents H-NMR data of the hasubanan alkaloids obtained since 1976. During the period 1976-1986, the application of H-NMR spectroscopy was accelerated together with the improvement of measuring instruments. NOE, INDOR, and two-dimensional NMR experiments (7) have been undertaken to resolve the question of stereochemistry at the chiral centers.

The configuration of roxburghine B, for which the normal ajmalicinoid stereochemistry had been postulated earlier, has now been re-examined by means of 300 MHz XH n.m.r. spectroscopy (combined with INDOR experiments),145 and 13Cn.m.r. spectroscopy.146 Whereas the 13C n.m.r. spectra of roxburghines D and E (pseudo), and C (normal) supported the previous assignments, neither the 13C nor the 300 MHz 3H n.m.r. spectrum supported the normal stereochemistry for roxburghine B, for which the epiallo-configuration (242) has now been established. 

Carbon-13 spectroscopy provides even more convincing evidence for the structure of the norbornyl cation. Using first (with White) the INDOR method10 and later (with Liang) the fast Fourier transformation method10, we obtained the com-... 

Due to the high receptivity of F, E nf correlation spectroscopy became available very early in the history of NMR spectroscopy. Using the INDOR technique on a cw-spectrometer, McFarlane and coworkers gave the first report whatsoever on the use of "X, "Y correlated spectroscopy for indirect observation via of the resonances in complexes of the type WF6 0R and WOp4L. Beside the first chemical shift determination for a low-7 transition metal, which was at that time not feasible by any other technique, further the indirect determination of y( W, P), and the assignment of relative coupling signs, was reported. 

High-resolution n.m.r. spectroscopy of D-glucobioses in deuterium oxide has shown that protons on, or vicinal to, the carbon atom involved in the glycosidic linkage are shifted downfield. De Bruyn s group has also assigned the 300 MHz H n.m.r. spectra of raffinose and melezitose (in DjO) and sucrose octa-acetate (in [ He]benzene and [ H]chloroform, etc.) with the help of homo-INDOR experiments. 

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