Efektivitas Gugus Pelindung ‒OH Fenolik pada Floroasetofenon dan 3,4- Dihidroksibenzaldehida dalam Upaya Menyintesis Kuersetin

Abstract

Quercetin is a of flavonol compound with hydroxylated A and B rings. Synthesis of this group of compounds is commonly through condensation reaction between hydroxylated acetophenoneand benzaldehyde derivatives and needs introduction of phenolic-OH protecting groups. In this study, tetrahydropyranylether (OTHP) and benzylether (OBn) were compared for their effectiveness in protecting the 2 phenolic‒OH groups in phloroactophenone and 3.4-dihydroxybenzaldehyde as the first step in quercetin synthesis. OTHP gave a huge steric hindrance so it could not protect the phenolic-OH of phloroacetophenone. On the contrary, OBn protected phloroacetophenone and 3,4-dihydroxybenzaldehyde more effectively. Two equivalent of BnBr in dimethylformamide after 24 hours, produced 2’,4’-di-Obenzylphloroacetophenone and 3,4-bis-(benzyloxy)benzaldehyde with 48% and 55% of yield, respectively. The condensation reaction between the two protected precursors produce mixture of products predicted to contain eriodictiol chalcone Bn-protected. Oxidative cyclization of the chalcone was yet to be succeeded to failed to form tetra-O-benzylquercetin. However, the effectiveness of OBn as a phenolic-OH protective group has been successfully demonstrated in this study