- Fluoride-Catalyzed Esterification of Amides
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In recent years, it has been demonstrated that amide carbon–nitrogen bonds can be activated and selectively cleaved using transition metal catalysts. However, these methodologies have been restricted to specific amides; a one-to-one relationship exists between the catalytic system and the amides and also uses large amounts of transition-metal catalysts and ligands. Hence, we now report a general strategy for esterification of common amides using fluoride as a catalyst. This method shows high functional group tolerance, and notably it requires only a slight excess of the alcohol nucleophile, which is a rare case in transition-metal-free amide transformations. Moreover, this approach may provide a new understanding for further studies on esterification of amides and is expected to stimulate the development of alternative methods for direct functionalization of amides.
- Wu, Hongxiang,Guo, Weijie,Daniel, Stelck,Li, Yue,Liu, Chao,Zeng, Zhuo
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p. 3444 - 3447
(2018/02/21)
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- Synthesis and antimicrobial activity of the essential oil compounds (E)- and (Z)-3-hexenyl nonanoate and two analogues
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Numerous studies and reviews on the subject matter of compounds isolated from plants have demonstrated that essential oil compounds display antimicrobial activity1-7. Of particular interest to this work is a study 8 where it was found that (Z)-3-hexenyl nonanoate 1a (Figure 1) was a major essential oil component (16 %) from Heteropyxis natalensis, a deciduous tree, from the family Heteropyxidaceae, having strongly aromatic foliage and being specific to the geographical location of Lagalametse in the Waterberg (Northern Province, South Africa). In addition, the (E)-isomer 1b has also been observed in plants, albeit in much lower amounts - see for instance the 0.2 % of this compound isolated from Cinnamomum tamala (Ham.) Nees & Eberm. 9 The authors of the South African study on Heteropyxis natalensis postulated that the particular (Z)-compound could be responsible for the overall antimicrobial properties of the essential oil. This hypothesis was based on a geographical variation study, whereby differences of antimicrobial activity were observed between varied regions. The most active (mean MIC value of 2.1 mg mL-1 against five test pathogens) of the Heteropyxis natalensis oil was evident where the major constituent comprised of (Z)-3-hexenyl nonanoate 1a. This compound was not present in any of the other geographical samples which had poorer activity (mean MIC value of between 4.0-7.4 mg mL-1 against the five test pathogens)8. Of interest is that compound 1a which has been associated with food additives; however, little else is known concerning the biological properties of these particular class of compounds. It was thus decided to synthesize compounds 1a and 1b, as well as two structural analogues 1c and 1d and test them for their putative antimicrobial efficacy.
- Chakravorty, Santanu,Rayner, Matthew K.,De Koning, Charles B.,Van Vuuren, Sandy F.,Van Otterlo, Willem A. L.
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p. 202 - 205
(2013/01/15)
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