7-Dehydroxylated derivates

The triterpene-enriched fraction of the supercritical CO2 extract of the dried flowers of Calendula officinalis (Asteraceae) inhibited the croton oil-induced ear edema in mice. Of the identified compounds, the faradiol monoesters, lupeol, F-taraxasterol and a mixture of taraxasterol/ 5-amyrin were tested for their anti-inflammatory activity. Faradiol, obtained by hydrolysis of the extract, was the most active compound. It showed a dose-dependent effect with a potency that equals that of indomethacin at 0.14 fimol/cm2 (48% and 47% edema inhibition, respectively). The esterification of faradiol resulted in a reduction of more than 50% in the activity (only 31% inhibition was observed at 0.14 pmol/cm2), whereas 4/-taraxasterol, a C-16P dehydroxylated derivative of faradiol, was less active (47% inhibition at a dose of 0.28 pmol/cm2) [43]. 

The tris-neopentyl Mo(VI) nitride, Mo(-CH2- Bu)3(=N) [134], reacts with surface silanols of silica to yield the tris-neopentyl derivative intermediate [(=SiO)Mo (-CH2- Bu)3(=NH)] followed by reductive elimination of neopentane, as indicated by labeling studies from labeled starting organometallic complex, to yield the final imido neopentylideneneopentyl monosiloxy complex [(=SiO)Mo(=CH- Bu)(-CH2 - Bu)(=NH)] [135]. The surface-bound neopentylidene Mo(VI) complex is an active olefin metathesis catalyst [135]. Improved synthesis of the same surface complex with higher catalytic activity by benzene impregnation rather than dichlorometh-ane on silica dehydroxylated at 700 °C has been reported [136],... 

When the dehydration of 39 was carried out (H3PO4 or DMSO under reflux) instead of its dehydroxylation, a different class of stilbene derivatives, such as pinosilvine 44, resveratrol 45 or piceatannol 46, were easily obtained . From these compounds, resver-atrol has shown very potent anticancer properties in vivo, this activity being proven in rats . 

The reaction is also useful for deacetoxylaton or dehydroxylation of a-oxygenated lactones derived from carbohydrates.160 (See entires 9 and 10 in Scheme 5.10.) Some other examples of this type of reaction are given in Scheme 5.10. Vinylogous oxygen... 

Hematite derived from dehydroxylation of FeOOH at temperatures below 600 °C shows marked, non-uniform (differential) broadening of the XRD lines. Some authors have attributed this effect to the anisotropic shape of the coherently diffracting domains of hematite (Duvigneaud Derie, 1980), and others to the development... 

The acid anhydride derived from the true hydrogen form, generally called dehydroxylated Y and assumed to be formed according to Reaction 3 of Uytterhoeven, Christner, and Hall (15). 

Basically, two different routes are conceivable for their asymmetric construction 1) nucleophilic substitution reaction with a fluoride anion and 2) electrophilic addition of fluoronium cations to activated or masked carbanions. First attempts on enantioselective nucleophilic fluorination date back to the pioneering work of Hann and Sampson [3]. In an ambitious dehydroxylation/fluorination sequence the authors reacted a racemic a-trimethylsiloxy ester with a half molar equivalent of an enantiomerically pure proline-derived aminofluorosulphurane in hope to achieve a kinetic resolution. Unfortunately, the fluorinated product was obtained without significant enantiomeric excess. 

The models based on desorption techniques are also able to derive the kinetic parameters of the dehydroxylation and dehydration processes. Also, the desorption energy (E,) for the different condensation processes can be calculated. Therefore, also energetically a distinction can be made between adsorbed water, free hydroxyls and bridged hydroxyls. 

The use of one-fourth an equivalent of phosphorus penta-chloride, in an attempt to utilize fully the dehydroxylating capacity of both phosphorus pentachloride and the derived phosphorus oxychloride, led to a low yield of diphenylbenzami-dine (50%) and to formation of tarry material that interfered with purification. By use of phosphorus oxychloride 4 instead of the pentachloride, a temperature of 170° was required to keep the mixture liquid, tarry material was considerable, and the operation was generally unsatisfactory. 

H30+ per gram and calculated pH values, for the filtrate samples, are shown in Table V. The molar H+/A1 ratio is also tabulated, demonstrating that a third of the proton sites are dehydroxylated by 400°C and another third by 700°C. This is further supported by the observation of decreased absorbance of the OH band at 3610 cm- in the infrared spectrum as the temperature is increased from 400°C to 800°C. Assuming that all strong acidity is derived from the exchange of H+ in the zeolite by Na+ in the concentrated NaCl solution, the filtrate pH is a direct measure of that exchange, using the simple relation pH = -log [H+]. For H30+-ZSM-5 calcined at 400°C, the filtrate sample titer is 0.431 meq. H30+/g of... 

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