Pulvinic amide

Formulation (43) shows the basic pulvinic acid carbon skeleton, and all known natural pulvinic acids show variations which include either hydroxylation of methoxylation of the benzene rings or lactonisations involving the carboxy function (Table 2). In addition, a few methyl ester and amide derivatives of the acids occur naturally. Early studies of the constitutions of pulvinic acids found in lichens have been summarized by Dean (7), and a useful account of pigments found in mushrooms, which includes pulvinic acid pigments, has been presented recently by Steglich 47). 

Although the pulvinic acid amide derivatives rhizocarpic acid and epanorin (58) could originate from simple coupling between the appropriate amino acid and the pulvinic acid, Maass (66) has proposed a direct route to pulvinamide itself (viz 58, R = H), involving condensation between phenylalanine and phenylpyruvic acid. 

Pulvinic acid derivatives now include calycin (108), epanorin (109), leprarinic acid, leprarinic acid methylester, pinastric acid (110), pulvinic acid (111), pulvinic acid amide, pulvinic acid lactone (112), and vulpinic acid. Taking calycin as an example, the UV maxima are at 241 (log,o6 = 4.20), 253 (logio e = 4.21), and 430 nm (logjo e = 4.40) (in ethanol). Pulvinic acid lactone may be synthesized simply by condensation of 2 molesphenylacetyl chloride (113) with oxalyl chloride (114). 

Rao PS, Raju KR (1989) Chemistry of Lichen Products Part VII. Some New Amide Derivatives from the Reaction of Acid Hydrazides with Pulvinic Dilactone. Current Sci (India) 58 444... 

---