From 4-Oxo-2-enoic Acids

In what amounts to a biogenetically patterned approach, a synthesis of xylerythrin (7 a) has been reported involving condensation between polyporic acid (100) and p-hydroxyphenylacetic acid (d) this Perkin-type reaction proceeds via the 4-oxo-2-enoic acid intermediate (101). 

The first synthesis of the carbon skeleton found in the lichen pulvinic acids (viz 43) was described by Volhard (92) as early as 1894. The synthesis begins with a substituted phenylacetonitrile which is first 

In other investigations of the synthesis of ylidenebutenolides from 4-oxo-2-enoic acid derivatives, Elvidge and co-workers 107) have shown that (110) and (112) are obtained, albeit in low yields, when the corresponding keto acids (109) and (111) respectively, are treated with acetic anhydride-hydrogen bromide. 

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