O-Methyltetronic acid

The application of 2-aryl O- methyltetronic acids (388) and (390) in the total synthesis of pulvinone pigments found in Aspergillus tereeus and Suillus grevillei has been reported. 

Regioselective reductions of the maleic anhydride derivatives (387) and (389) with lithium aluminum hydride yielded (388) and (390). Metallation of the O-methyltetronic acid (388) with lithium N- cyclohexyl-A- isopropylamide followed by treatment with, for example, p-anisaldehyde led to pulvinones such as (391) (79JCS(P1)70). 

Tetronic Acids.—The vinyl lithium species (102) reacts with aldehydes to provide a quick if not particularly efficient (11—57% yields) entry into O-methyltetronic acids (103), which can be converted into the ylidenetetronic acids (104) by standard methodology (LDA, PhSSPh, and oxidize 32—40% yield).Both (103) and (104) give the free tetronic acids on reaction with 48% HBr. It has been re-emphasized that tetronic acids can be O-alkylated using methanol (or ethanol) and hydrogen chloride. 

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See also in sourсe #XX -- [ ]

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