Metalation of 1‐methylpyrrole using n‐butyllithium and tetramethylethylenediamine (TMEDA) in ether furnished 1‐methyl‐2‐pyrrolyllithium, which in turn was converted to 1‐methyl‐2‐methylthiopyrrole upon treatment with dimethyldisulfide. Further formylation with dimethylformamide, phosphorus oxychloride in dichloroethane led to the corresponding pyrrole‐2‐carboxaldehyde, which was then condensed with malononitrile and methylcyanoacetate under Knoevenagel reaction conditions to give 2‐cyano‐3‐(1‐methyl‐5‐methylthio‐2‐pyrrolyl)acrylonitrile and 2‐cyano‐3‐(1‐methyl‐5‐methylthio‐2‐pyrrolyl)acrylic acid methyl ester, respectively. Their oxidation by hydrogen peroxide furnished the corresponding sulfones. Analogously, 5‐phenylthio derivatives were prepared.
The studied 1-(2-benzothiazolyl)-2-pyridones Va-Vf were prepared from N-(2-benzothiazolyl)cyanoacetamide (II) which on reaction with 4-substituted benzaldehydes afforded 3-aryl-N-(2-benzothiazolyl)-2-cyano-2-propenamides IVa-IVg. Compounds IVa-IVf were cyclized with malonodinitrile in the presence of piperidine to give the corresponding pyridones Va-Vf.
Substituted 1-(6-methoxy-2-benzothiazolyl)-2-pyridones 5a-5f have been prepared from N-(6-methoxy-2-benzothiazolyl)cyanoacetamide (2) which on reactions with 4-substituted benzaldehydes gives 3-aryl-2-cyano-N-(6-methoxy-2-benzothiazolyl)-2-propenamides 4a-4g. Derivatives 4a-4f were cyclized with malonodinitrile in the presence of piperidine to give the corresponding 2-pyridones 5a-5f. The IR, UV, 1H NMR and mass spectra of the substances synthesized are discussed.
The reaction of 5-X-2-furaldehydes (X = C6H5, COOCH3, COOC2H5, C6H5O, C6H5S, CH3S, 4-Cl-C6H4S, CH3SO2, C6H5SO2, 4-Cl-C6H4SO2) with ethyl cyanoacetate in dry ethanol catalyzed by sodium ethoxide yielded the corresponding ethyl 2-cyano-3-(5-X-2-furyl)acrylates. It was found that the reactions of these esters with cyanoacetophenone or ethyl acetoacetate do not afford the corresponding 4H-pyran derivatives but that there proceeds the exchange of ethyl acetoacetate or of ethyl cyanoacetate for the cyanoacetophenone carbanion. The same course has been observed also for the reactions of these substrates with malononitrile.
Five streptomycins bleached the chloroplast system of Euglena gracilis; the most effective were those which contained an aldehyde group in the streptose moiety: streptomycin and hydroxystreptomycin. Derivatives containing a secondary alcohol group in place of the aldehyde (dihydro-, dihydrodesoxy-, dihydrohydroxystreptomycin) require higher concentrations to elicit the same effect. Hydroxylamine reversed the bleaching effects of streptomycin and hydroxystreptomycin but not of dihydro-, dihydrodesoxy-or dihydrohydroxystreptomycin. These observations suggest that the aldehyde group of the streptomycins contributes to the action of these antibiotics on Euglena chloroplasts; the action of hydroxylamine would be to either remove the antibiotic from its site of action or to render it ineffective in vivo by reaction with the aldehyde group.
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