The Total Synthesis of Some Natural Products

Abstract

The work presented in this thesis consists of Total synthesis of Desmethyldiaportinol and Trilepisumic acid which are naturally occurring isocoumarin and derivative of caffeic acid respectively. Desmethyldiaportinol was synthesized in 17 steps. 3,5- Dimethoxyhomopthalic acid was synthesized starting from commercially available 3,5-Dihydroxybenzoic acid and then it was condensed with 3,4- Dibromobutanoyl chloride which was itself synthesized starting from allyl bromide to yield 3-(2,3-Dibromopropyl)-6,8-dimethoxyisocoumarin. The conversion of bromides into hydroxyl groups were carried out by refluxing in a mixture of acetone and water. Finally demethylation was achieved by refluxing in 33% HBr to yield the required compound. Trilepisumic acid was synthesized in 4 steps starting from the condensation of 3,4-Dimethoxybenzaldehyde with malonic acid to yield 3,4- Dimethoxycinnamic acid. Esterification was carried out by treatment with vanillin and then the formyl group was oxidized into acid by using one equivalent of KMnO4 in acidic medium. Finally demethylation was achieved by refluxing in 33% HBr to yield the required compound. The structures of all the compounds were confirmed by FTIR, 1HNMR and 13CNMR spectroscopy.