Spectroscopy conformational analysis

CUMULATIVE INDEX, VOLUMES 1-13 Infrared Spectroscopy, Conformational Analysis of Intramolecular Hydrogen-Bonded Compounds in Dilute Solution by (Aaron). VOL. 11 487 PAGE 1... 

A conformational analysis of furanoid - pyranoid non-reducing disaccharides, based on crystallographic data, has been published, and the conformation of trehalose incorporated in a micelle has been studied by H-n.m.r, spectroscopy. Conformational analysis by use of various and C-n.m.r. techniques in combination with theoretical calculations has been achieved for the two galactobiosides (18) and (19), for the eight-membered 3,2 -O-isopropylidene acetals (20) and (21) of methyl / -cellobioside and benzyl -D-lactoside, respectively. 

The physical, chemical cind biological properties of a molecule often depend critically upo the three-dimensional structures, or conformations, that it can adopt. Conformational analysi is the study of the conformations of a molecule and their influence on its properties. Th development of modem conformational analysis is often attributed to D H R Bcirton, wh showed in 1950 that the reactivity of substituted cyclohexanes wcis influenced by th equatoricil or axial nature of the substituents [Beirton 1950]. An equcilly important reaso for the development of conformatiorml analysis at that time Wcis the introduction c analytic il techniques such as infreired spectroscopy, NMR and X-ray crystaillograph] which actucilly enabled the conformation to be determined. 

Application of NMR spectroscopy to heterocyclic chemistry has developed very rapidly during the past 15 years, and the technique is now used almost as routinely as H NMR spectroscopy. There are four main areas of application of interest to the heterocyclic chemist (i) elucidation of structure, where the method can be particularly valuable for complex natural products such as alkaloids and carbohydrate antibiotics (ii) stereochemical studies, especially conformational analysis of saturated heterocyclic systems (iii) the correlation of various theoretical aspects of structure and electronic distribution with chemical shifts, coupling constants and other NMR derived parameters and (iv) the unravelling of biosynthetic pathways to natural products, where, in contrast to related studies with " C-labelled precursors, stepwise degradation of the secondary metabolite is usually unnecessary. 

The isoxazolidine ring exists primarily as an envelope (77AHQ2l)207) and the nitrogen lone pair can occupy an axial or equatorial position. Photoelectronic spectroscopy is a useful tool to determine conformational analysis of molecules possessing vicinal electron lone-pairs. Rademiacher and Frickmann (78TL841) studied isoxazolidine and 2-methyl- and 2-t-butyl-isoxazolidine and found mixtures of equatorial and axial (e/a) compounds. The ratios of H, Me and Bu in the efa position were 1 3, 4 1 and 10 1, respectively. 

Conformational Analysis of Drugs by Nuclear Magnetic Resonance Spectroscopy... 

Nuclear magnetic resonance (NMR) spectroscopy is, next to X-ray diffraction, the most important method to elucidate molecular structures of small molecules up to large bio macromolecules. It is used as a routine method in every chemical laboratory and it is not the aim of this article to give a comprehensive review about NMR in structural analysis. We will concentrate here on liquid-state applications with respect to drugs or drug-like molecules to emphasize techniques for conformational analysis including recent developments in the field. 

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