Structure elucidation INDEX

The antimalarial properties attributed to preparations from Dichroa febrifuga by the Chinese were confirmed about 1944 and two alkaloids, febrifugine (999) and isofebrifugine (1000), were isolated eventually. After difficult structural elucidations, syntheses of ( )-febrifugine followed it proved to be half as active as the natural material, itself far better than quinine, but the therapeutic index was disappointingly low (67HC(24-l)490). 

Typically, sample detection in electromigration techniques is performed by on-column detection, employing a small part of the capillary as the detection cell where a property of either the analyte, such as UV absorbance, or the solution, such as refractive index or conductivity, is monitored. This section briefly describes the major detection modalities employed in capillary electromigration techniques, which are accomplished using UV-visible absorbance, fluorescence spectroscopy, and electrochemical systems. The hyphenation of capillary electromigration techniques with spectroscopic techniques employed for identification and structural elucidation of the separated compounds is also described. 

An example for a GC-analysis of isolated sterols from P. oryzae is shown in Figure 8. An elution diagram of an untreated control is compared to the sterol analysis after application of 10 ppm triadi-menol. It can easily be seen that in the region where the sterols are eluted (framed area), the pattern becomes totally different. The elution index is the first criterion for the chemical nature of an accumulating sterol. However, structure elucidation has been per-... 

In the tables are given only recent references which directly pertain to alkaloid isolation and structural elucidation and which have not appeared in the above tabulations and reviews. The absence of reference number for particular alkaloid types implies that the original paper(s) may be found by searching the indexes of these works under the corresponding plant species which contain them. 

Artemisinin 1, a naturally occurring sesquiterpene peroxy-lactone, has been isolated in up to 0.25% yield from the dry leaves of Artemisia annua L.1 Interest in artemisinin is based on its phytomedicinal properties. In 168 b.c. China, as described in a Treatment of 52 Sicknesses, the leaves of A. annua (Qinghao) were used for the treatment of chills and fever.2 It was not until 1972 that the active antimalarial agent qinghaosu was isolated in pure form. This allowed for the unequivocal elucidation of its structure through the use of x-ray crystallography. This complex tetracyclic peroxide is now referred to as artemisinin in various sources such as Chemical Abstracts or the Merck Index. 

HPLC with UV detection at 280 nm showed essentially only the required drug compound but a quantitative assay against a reference material showed a level of only 96.6% of that expected. A number of impurities were detected by using HPLC with MS and refractive index detection and the structures of the major components were elucidated by using 500 MHz H HPLC-NMR spectroscopy. 

The international tests have shown that a GC/ FTIR instrument is not a necessity for successful testing because two other techniques (GC/EI/MS, GC/CI/MS, NMR, or even GC retention index monitoring) can be used as the required different techniques. The major advantages of GC/FTIR are that it gives information on different characteristics of a chemical than, for example, MS and NMR. Therefore, it can make the overall spectral elucidation easier and faster. Also, the first guesses , that is, candidate structures for synthesis are more accurate when FUR is used (see ref. (25) for examples). The latter advantage is emphasized when analyzing phosphorus chemicals. 

Clarifying the structure and functions of protein materials in the solid state provides an index with respect to the design of artificial biomaterials. Solid-state NMR has been used as a powerful means for elucidating structure and dynamics in addition to the X-ray diffraction method [le]. The structure and dynamics of some fibrous proteins, such as wool, silk, collagen, tropomyosin, etc., have been characterized using characteristic solid-state NMR chemical shifts as stated above, and much more new information obtained in addition to the results provided by X-ray diffraction. And the individual advantages of these two methods are complementary with each other. Details of appli-... 

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