Pulvinic acid lactone derivatives

Apart from the A-methylated compound,1 examples for derivatives of the fully conjugated pyridazino[4,3-c]pyridazine or the unsubstituted compound 1 itself are not known. Attempts to synthesize 4,8-diphenylpyridazino[4,3-c]pyridazine-3,7-diol (3) by reacting pulvinic acid lactone 2 with an excess of hydrazine failed, instead 6-benzyl-4-phenylpyridazine-3,5-diol (4) was produced. The reaction is thought to proceed via the attack of hydrazine on one lactone ring and water on the other, followed by decarboxylation.4... 

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). 

Raju KR, Rao PS (1986) Chemistry of Lichen Products. Part VI - Synthesis of Some New Benzimidazole Derivatives from Pulvinic Acid Lactone and their Fungicidal Activity. Indian J Chem B 25 97... 

A unique pulvinic acid derivative, methyl bovinate (98), which contains an extra carbon atom in the form of the carbonyl group of an additional 5-lactone ring has been isolated by Besl et al. from cultures of Suillus bovinus 99). Its structure followed from the spectroscopic data, particularly the proton coupled C-n.m.r. spectrum. 

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