6615-01-6Relevant academic research and scientific papers
Transition-metal catalyzed oxidations. 7. Zirconium-catalyzed oxidation of primary and secondary alcohols with hydroperoxides
Krohn, Karsten,Vinke, Ingeborg,Adam, Horst
, p. 1467 - 1472 (1996)
A new procedure for the oxidation (dehydrogenation) of primary and secondary alcohols employing Zr(O-t-Bu)4 or Zr(O-n-Pr)4/tert-butyl hydroperoxide/3 A molecular sieves is presented. Secondary alcohols - if not severely sterically hindered - are usually converted quantitatively to the corresponding ketones. Esters or acids can be by products in the reaction of primary alcohols. However, the aldehydes are obtained in good yield by lowering the reaction temperature, decreasing the amount of TBHP or replacing TBHP by cumene hydroperoxide (CHP), and/or exchanging the catalyst Zr(O-t-Bu)4 by Zr(O-n-Pr)4 or silica gel-supported Zr(OR)(x). A remarkable selectivity of equatorial alcohol groups (e.g., 11 and 13) is observed in contrast to chromium(VI)-based oxidations. Strongly chelating substrates such as furfuryl alcohol (18) or 1,2-diol 25 that prevent hydride transfer in the six-membered transition state A are not converted.
Synthesis of RNAse active site model systems using a steroid template
Kalesse,Oost
, p. 89 - 99 (2007/10/03)
The evaluation of RNAse active site model systems based on rigid steroid templates is described. Our preliminary work on steroid derived RNAse model systems showed that preorientation of guanidinium groups and one imidazole moiety leads to active compounds. We found that within the corticosterone derived steroid series, the C11-α-configurated compounds were superior to their β-diastereomers. In order to evaluate the influence of the conformational flexibility of the imidazole group, a flexible side chain was introduced at C17. The fact that this more flexible imidazole group leads to a decrease in the hydrolytic behavior of the steroid derivative further validates our approach of establishing a preorientated RNAse model system for an efficient RNA hydrolysis.
11-Difluoromethylene steroids
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, (2008/06/13)
11-Difluoromethylene steroids having progestational and anti-progestational properties, useful as anti-fertility agents, are disclosed as well as a process for making the 11-difluoromethylene steroids.
11β-Difluoromethyl and (E)- and (Z)-11-fluoromethylene steriods
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, (2008/06/13)
Known reactions are arranged in a novel manner to produce 11β-difluoromethyl and (E)- and (Z)-11-fluoromethylene 19-norandrostenediones and 19-nor-13β-ethylandrostenediones which are useful as contraceptive agents.
