Pulvinic acid lactone

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). 

Pulvinic acid lactone Drechslera rosiraia, Allernaria alternata (601-603,... 

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... 

Tryptophan and its relative indolylpyruvic acid (3.42) have been shown to precursors of hinnuliquinone (3.41), which is a pigment of Nodulisporium hin-nuleum. Typical of many fungal indoles in which alkylation by a dimethylallyl or isopentenyl group has occurred, mevalonate was also a precursor. However, the stage at which prenylation of a monomer or a dimer took place was unclear. Asterriquinone (3.43) from Aspergillus terreus and cochliodinol (3.44) from Chaetomium cochliodes are similar metabolites. Fission of the hydroxyquinone in the latter followed by lactonization leads to cochliodinone (3.45) in a sequence that is similar to that which inter-relates the terphenyls and pulvinic acids described in Chapter 7. 

Patenden et al. [46] synthesized heterocyclic analogues of pulvinones 52-55 and of permethylated pulvinic acids 56, 57 which were found in higher fungi (Scheme 21). All compounds possessing lactonic structures were synthesized in the Horner-Wittig reaction using the corresponding heteroaryl aldehydes and 4-dimethoxy-phosphorylated lactone 58. The latter was obtained as the main product in the reaction between substituted maleic anhydrides 59 and sodium dimethyl phosphite via the postulated carbene. 

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. 

Ramage and coworkers (537) have developed a biomimetic synthesis of pulvinic acids which relies for its success on the facility with which dioxolanones of type (110) undergo nucleophilic attack at the lactone carbonyl group with subsequent extrusion of cyclohexanone. In the synthesis of xerocomic acid (Scheme 15) the dioxolanone (110), obtained as the predominant isomer from reaction between the phos-phorane (109) and methyl (3,4-dibenzyloxyphenyl)glyoxalate, was cleaved with the lithium enolate of /-butyl (4-benzyloxyphenyl)acetate. The intermediate dianion (111) probably exists at first as the chelate (112) which is then broken down on aqueous work up and subsequently cyclised specifically at the less hindered carbonyl group to produce the ester (113). The dianion (111) is analogous to the hypothetical... 

Metabolism of the Aromatic Amino Acids 175 occur together it is conceivable that the quinones are the biogenetic precursors of the pulvinic acid compounds. Indeed such conversions can be carried out oxidatively in the laboratory and tracer experiments in Pseudocyphellaria crocata have indicated that poly-poric acid (127) can act as a precursor of pulvinic lactone (132). ... 

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