Nuclear magnetic resonance bioactive compounds

Similarly to the above section, no additional specific nuclear magnetic resonance (NMR) data have been published since CHEC(1984) and CHEC-II(1996) <1996CHEC-II(8)249> NMR data for new substituted compounds are routinely reported. Several X-ray structures of bioactive molecules possessing this heterocyclic core have been reported C1999BML1979, 1999JME779>. 

Use of an integrated system incorporating CCC separation, PDA detector, and LC-MS proved to be a valuable tool in the rapid identification of known compounds from microbial extracts.6 This collection of analytical data has enabled us to make exploratory use of advanced data analysis methods to enhance the identification process. For example, from the UV absorbance maxima and molecular weight for the active compound(s) present in a fraction, a list of potential structural matches from a natural products database (e.g., Berdy Bioactive Natural Products Database, Dictionary of Natural Products by Chapman and Hall, etc.) can be generated. Subsequently, the identity of metabolite(s) was ascertained by acquiring a proton nuclear magnetic resonance ( H-NMR) spectrum. 

Metaferia et al. reported on the synthesis and cytotoxicity of C3 -C4 linked macrocyclic taxoids in 2001. The synthetic strategy was also based on RCM. Similar to Ojima et al. s finding, these compounds (100) are less active than paclitaxel in both cytotoxicity and tubulin assays.However, after careful inspection of the bioactive conformations of taxoids with computer simulation and nuclear magnetic resonance (NMR) experiments, they designed several C-4 and C3 -Ph orf/io-position linked taxoids (101) that were highly active, several times better than paclitaxel. ... 

The wide range of spectroscopic techniques such as UV, infrared (IR), Gas Chromatography-Mass Spectroscopy (GC-MS), Liquid Chromatography-Mass spectra (LC-MS), Nuclear Magnetic Resonance (NMR), and mass spectra (MS) form the backbone of modem stmctural elucidation studies as mentioned in the Figure 8.2. Prior to the availability of such advanced techniques, ambiguities existed in the determination of stmctures of bioactive compounds. The process of spectroscopic determination should be closely allied to familiarity with the scientific literature. If the compound has not been described, it may be very similar to reported compounds and that may assist in the interpretation of data for the unknown. In this regard, an awareness of the coextractives from the plant may also be of value to determine the stmctures. 

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