Optical techniques spectral isolation

Stylotelline (23) is a constituent of a Stylotella sp. collected offshore in New Caledonia. 13C NMR spectra involving 2D NMR techniques provided the bulk of information leading to its structure. The absolute configuration was demonstrated after the tertiary isocyano group was removed to yield the known conjugated diene, ( + )-d-selinene (24). Optical rotation and spectral data of the transformation product were identical in all respects to those of the corresponding product obtained from eudesmols [42], Although neither the isothiocyanato nor the formamido compounds were isolated, the latter was prepared, which allowed an nOe observation between the axial C-3 and the amide protons. 

To determine the oil, water, and solids contents simultaneously, sophisticated statistical techniques must usually be applied, such as partial least-squares analysis (PLS) and multivariate analysis (MVA). This approach requires a great deal of preparation and analysis of standards for calibration. Near-infrared peaks can generally be quantified by using Beer s law consequently, NIRA is an excellent analytical tool. In addition, NIRA has a fast spectral acquisition time and can be adapted to fiber optics this adaptability allows the instrument to be placed in a control room somewhat isolated from the plant environment. 

Terpenoids can be analyzed by the usual methods. For the volatile members of the family, gas chromatography-mass spectrometry (gc-ms) is a particularly useful tool. In laboratories (e.g., those in the major fragrance companies), which are accustomed to analyzing mixtures of volatile terpenoids, gc-ms is the major analytical technique employed and such laboratories will have extensive libraries of mass spectra of terpenoids to assist in this. However, the mass spectral fragmentation patterns of closely related terpenoids are often so similar as to render definitive identification by ms alone, impossible. For these materials and those for which there is no reference (e.g., compounds newly isolated from nature), nuclear magnetic resonance (nmr) spectroscopy is the analytical tool of choice. Physical techniques, e.g., density, refractive index, and optical rotation, are relatively inexpensive and prove useful in quality control. 

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