Synthesis of Methyl 5-Aryl-3-oxo-4-pentenoates and Novel Substituted Cyclopentenones
作者:C. V. Asokan、S. Bhattacharji、H. Ila、H. Junjappa
DOI:10.1055/s-1988-27543
日期:——
The cinnamoyl- (1a-j) and (5-phenyl-2,4-pentadienoyl)- (1k) ketene dithioacetals are shown to undergo methanolysis in the presence of ether-boron trifluoride complex and mercury(II) chloride to the corresponding methyl 5-aryl-3-oxo-4-pentenoates 2a-j and 3-oxo-7-phenyl- 4,6-heptadienoate (2k), respectively, in good yields. However, the corresponding (2-methylcinnamoyl)ketene dithioacetals 3a-f, under identical reaction conditions, undergo Nazarov cyclization to give the corresponding substituted cyclopentenones 4a-f.
α-acylketene dithioacetals in refluxing benzene affords α-acetoxyketene dithioacetals as major products which could be hydrolyzed to α-diketone dithioacetals under mild alkaline conditions. Under similar oxidative conditions, α-cinnamoyl ketene dithioacetals yield 2-acetoxycyclopentenone derivatives through an interesting oxidative Nazarov cyclization involving intermediate α-acetoxy dithioacetals accompanied
Polarized Ketene Dithioacetals; 55:<sup>1</sup>Synthesis of Novel 5-Aryl-2-methylthio-4<i>H</i>-pyran-4-ones from Cinnamoylketene Dithioacetals
作者:B. Deb、C. V. Asokan、H. Ila、H. Junjappa
DOI:10.1055/s-1987-28112
日期:——
A novel method for the synthesis of 5-aryl-2-methylthio-4H-pyran-4-ones 4a-h has been developed from the corresponding cinnamoylketene dithioacetals 1a-h in three successive steps. In the first step, 1a-h were oxidized with alkaline hydrogen peroxide to give the corresponding (β-aryl-,α,β-epoxypropanoyl)ketene dithioacetals 2a-h in 78-89% overall yields. In the second step the epoxyketones 2a-h were subjected to rearrangement in the presence of ether-boron trifluoride complex to give the corresponding (α-formyl-α-phenylacetyl)ketene dithioacetals 3a-h, which were then cyclized in the third step by refluxing in acetic acid/ethanol to afford the title compounds in good yields.
A series of substituted aryl pyrimidine derivatives was synthesized and evaluated in vitro for their antileishmanial potential against intracellular amastigotes of Leishmania donovani using reporter gene luciferase assay. Among all, 8 compounds showed promising IC50 values ranging from 0.5 to 12.9 mu M. Selectivity indices (S.I.) of all these compounds are far better than reference drugs, sodium stibogluconate (SSG) and miltefosine. On the basis of good S.I., compounds were further screened for their in vivo antileishmanial activity against L. donovani/hamster model. Compounds 2d, 4a and 4b have shown significant inhibition of parasitic multiplication that is 88.4%, 78.1% and 78.2%, respectively at a daily dose of 50 mg/kg x 5 days, when administered intraperitoneally. Compound 2d is most promising one, which may provide a new lead that could be exploited as a new antileishmanial agent. (C) 2013 Elsevier Ltd. All rights reserved.