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 P-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-6methyl benzoate (29), 2,4-dimethoxy-6-methyl biphenyl (31 ), and 6-(2,4-dimethoxy-6-methyl phenyl) -4-met hoxy-2H-pyran-2-one (34).

Biomimetic Approach Toward Enterocin and Deoxyenterocin

“…Afterward, the reaction was directly purified by FCC (EtOAc/ i -hex 2:1 then MeOH/EtOAc 4:96) to afford phosphonate 19 (0.26 g, 0.92 mmol, quant.) as a white solid …”

“…as a white solid. 26 R f : 0.3, MeOH:EtOAc 4:96, KMnO 4 , UV. 1 H NMR (400 MHz, CDCl 3 ): δ = 6.01 (t, J = 2.9 Hz, 1H), 5.45 (d, J = 2.1 Hz, 1H), 3.82 (s, 3H), 3.80 (d, J = 3.2 Hz, 6H), 3.04 (d, J = 22.0 Hz, 2H).…”