5-Methoxyphenanthrene-4-carboxylic Acid

Lead tetraacetate oxidation of phenanthrene-4,5-dicarboxylic acid in acetonitrile with pyridine affords 5-hydroxyphenanthrene-4-carboxylic acid as its lactone , which can be methylated as the sodium salt, giving 5-methoxyphenanthrene-4-carboxylic acid, albeit in poor yield. New spectroscopic evidence (particularly 13C n.m.r.) confirms that 5-formylphenanthrene-4-carboxylic acid, which is an intermediate in the synthesis, exists as the lactol , 4-hydroxyphenanthro[4,5-cdeloxepin-G(4H)-one.