Synthesis and purification of 7-prenyloxycoumarins and herniarin as bioactive natural coumarins

ABSTRACT

7-prenyloxycoumarins including 7-isopentenyloxycoumarin, auraptene and umbelliprenin, and herniarin have been widely recognized as bioactive coumarins. This paper presents the ways to synthesis these compounds. 7-prenyloxycoumarins were synthesized by reaction between 7-hydroxycoumarin [1 M] and relevant prenyl bromides [1.5 M] in acetone at room temperature. The reaction was carried out in the presence of DBU [1, 8-diazabicyclo [5.4.0] undec-7-ene] [2 M]. After 24 hr. the mixture was concentrated under reduced pressure. The compounds were purified by column chromatography. Three bioactive 7-prenyloxycoumarins, namely, umbelliprenin, auraptene and 7-isopentenyloxycoumarin, together with herniarin were synthesized from 7-hydroxycoumarin under alkaline conditions [DBU] and then purified by column chromatography. The structures of the products were characterized by NMR spectroscopic method including [1]H- and [13]C-NMR experiments. The method of synthesis for 7-prenyloxycoumarins and herniarin which is presented here has not been reported yet. Moreover, for the first time, umbelliprenin was chemically prepared in this work