Synthesis, spectroscopic and anti‐tumor studies of polyphenol‐linoleates derived from natural polyphenols

Abstract

AbstractAn efficient first synthesis of di‐, hexa‐ and octa‐esters (octadeca‐Z‐9,12‐dienoates, linoleates) from natural 1,5‐bis‐(4'‐hydroxyphenyl)penta‐Z‐1,4‐diene (Ginkgo biloba L.), (–)‐epigallocatechin and (–)‐epigallocatechin‐3‐O‐gallate (jasmine tea/green tea), respectively, was developed. Using dicyclohexyl carbodiimide as an activating reagent in the presence of a catalytic amount of 4‐dimethylaminopyridine in polyesterification reactions gave di‐, hexa‐ and octa‐products (4), (7), and (8), respectively, in quantitative yields. A three‐step efficient procedure for the synthesis of 1,5‐bis‐[4'‐O‐(octadec‐Z‐9”,12”‐dienoate)phenyl]penta‐Z‐1,4‐diene (4) was also developed. The key step in the synthesis involved a stereo selective Wittig diolefination reaction that produced the penta‐Z‐1,4‐diene system of (4). 1H and 13C NMR and MS techniques confirmed the structures of the esters. The esterified compounds were tested for in vitro anti‐tumor activities against four and three human cancer cell lines at NCNPR and at NCI, respectively. They were found inactive as they failed to inhibit 50% growth of these cancer cells.