Syntheses And Antibacterial Screening Of Juglone Derivatives
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Date
2010-11
Authors
Tan, Daniel Teoh Chuan
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Publisher
Universiti Sains Malaysia
Abstract
The juglone natural product has been used as the starting material in the syntheses of various bioactive quinones like ochromycinone. The present study involves the syntheses of juglone derivatives from both juglone and non-juglone starting materials. The ochromycinone precursor, 1,2,3,4-tetrahydro-8-hydroxy-3-methylbenz[a] anthracene-7,12-dione (19) was synthesised from juglone in two steps. The first step was the Diels-Alder reaction and the second step was the aromatisation reaction. In addition, a new para-nitrojuglone derivative (51) was obtained as the sole isomeric product from the direct nitration of juglone. The reaction involved the use of nickel(II) nitrate as the nitrating agent. The Friedel-Crafts acylation reactions between various 4-halophenol derivatives and maleic anhydride were also carried out. The acylation reactions yielded five 8-halojuglone derivatives (30, 31, 52, 53 and 54), two of which (52 and 54) are new derivatives. One of the acylation reactions afforded an anthraquinone (69) as the minor product. The anthraquinone (69) was later identified as the known naturally-occurring helminthosporin. All of the synthetic juglone derivatives were assayed against two Gram-positive and two Gram-negative bacterial strains. 8-Nitrojuglone (51) exhibited significant activity against the Gram-positive S. aureus bacteria. Furthermore, helminthosporin (69) displayed the highest activities against both of the Gram-negative bacteria assayed. However, all of the 8-halojuglone derivatives (30, 31, 52, 53 and 54) showed lower antibacterial activities than those of juglone.
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Keywords
Syntheses of juglone derivatives from both , juglone and non-juglone starting materials