Biomimetic syntheses of polyketide aromatics from pyrylium salts

Abstract

Following attack by nucleophiles, various methoxypyrylium compounds derived from 2H-pyran-2-ones and 4H-pyran-4-ones react either to produce a linear β-polycarbonyl derivative in which one or more carbonyl groups is derivatised in the form of an enol ether or to form a methylene-2H-pyran. The linear polycarbonyl derivatives can undergo biomimetic cyclisation to generate polyketide aromatic systems; syntheses of the following benzene derivatives are described: ethyl 2,4-dimethoxy-6-methylbenzoate (29), 2,4-dimethoxy-6-methylbiphenyl (31), and 6-(2,4-dimethoxy-6-methylphenyl)-4-methoxy-2H-pyran-2-one (34).