investigation on methylation methods of hesperidin

Since hesperidin is a poor water soluble compound, in pharmaceutical formulations its methylated derivatives [hesperidin methyl chalcone, HMC] are used. The aim of this study was to establish an efficient methylation method for preparation of hesperidin methyl derivatives. For this purpose hesperidin was isolated from tangerine peel, purified and its methyl derivatives were prepared using three different techniques, i.e. diazomethane, methyl iodide-sodium hydride and dimethylsulfate. The efficiency of the methods was evaluated in terms of the percentage of unchanged and intact hesperidin in the final methylated products the and amount of unchanged hesperidin was an indication of the better efficiency of the method. A reversed phase HPLC method was also developed for determination and quantification of hesperidin in the final methylated products.The method involved the use of a Shim pack CLC-ODS column, a mixture of methanol-phosphate buffer [37:63, v/v] of pH = 2.6 as a mobile phase in an isocratic mode at a flow rate of 1 ml/min and UV detection at 280 nm. The results showed that methylation with methyl iodide-sodium hydride have the highest efficiency among different methylation methods

Ethoxycarbonylmethylation of 3- [1-penylhydrazono-L-threo-2,3,4-trihydroxybutyl] -1H-quinoxalin-2-one

Reaction of 3-[1-phenylhydrazono-L-threo-2, 3, 4-trihydroxybutyl]-1H- quinoxalin-2-one [I] with ethyl chloroacetate gave 1-ethoxycarbonylmethyl-3-[phenylhydrazonon-L-threo-2, 3, 4-trihydroxybutyl]-1H-quinoxalin-2-one [III] and 1-ethoxycarbonylmethyl-3-[5-hydroxymethyl-1-phenylpyrazol-3-y]-1H- quinoxalin-2-one [IV]. Their proportion was dependent upon the conditions of the reaction. Acetylation of compounds III and IV afforded the corresponding acetylated products V and VI, respectively. Periodate oxidation of III gave I- ethoxycarbonylmethyl-3-[1-phenylhydrazono-glyoxal-1-yl]-1H- quinoxalin-2-on [VII]. Condensation of IV with hydrazine hydrate gave 1-hydrazinocarbonylmethyl-3-[5-hydroxmethyl-1-phenylpyrazol-3-yl]-1H- quinoxalin-2-one [VIII], whose reaction with benzaldehyde gave the corresponding hydrazone IX

Methylation of 3- [1-arylyhdrazono-L-threo-2,3,4-trihydroxybutyl] 6,7-dimeth yl-1H-quinoxalin-2-ones

Several N-methyl derivatives of 3-[1-arylhydrazono-L-threo-2, 3, 4- trihydroxybutyl]-6, 7-dimethyl-1H-quinoxalin-2-ones were prepared and converted to 3-[5-[acetoxymethyl]-1-arylpyrazol-3-yl]-1, 6, 7 -trimethylquinoxalin-2-ones. Upon deacetylation, compound VIII and IX gave products identical with those obtained by methylation of 3-[1- aryl-5-[hydroxymethyl]-pyrazol-3-yl]-6, 7-dimethyl-1H-quinoxalin -2- ones