Synthesis of 4′-O-methyl- and 4′,6-di-O-methyl-chalaurenol

Abstract

Syntheses are described, of the 4′-O- and 4′,6-di-O-methyl ethers of chalaurenol (1), a novel quinol enol ether obtained from peroxidase enzyme oxidation of the important rotenoid and flavonoid precursor, 2′,4,4′-trihydroxychalcone. Aryl orthoformate (12) was condensed with the enol ethers (6) and (7), with trimethylsilyl trifluoromethanesulphonate as catalyst, to yield the acetals (13) and (14), which when heated in pyridine gave the desired ethers (15) and (16). Hoesch conditions using the aryloxy oxo nitrite (24) were unsuccessful, leading to attack at the carbonyl carbon.