Pulvinic dilactone

Screening pigments Pulvinic dilactone Pulvinic acid derivative 1672 1405 >246 290 367 431 422... 

The hydroxylated pulvinic acids such as variegatic acid (73) may be characterised in the form of their dilactone peracetates, e.g. (75) (Scheme 10), which exhibit sharp melting points, in contrast to the parent pigments, and give rise to diagnostic infrared absorption above 1800 cm 73). Dilactone formation also occurs on electron impact and the mass spectral fragmentation of pulvinic dilactones has proved valuable in structural elucidation 452, 453, 607, 608). On treatment with diazomethane the hydroxypulvinic acids are converted into the... 

Symmetrically substituted pulvinic dilactones are conveniently obtained from terphenylquinones by oxidative ring cleavage. This may be brought about with hydrogen peroxide 425), with lead tetra-acetate 248) or best with dimethyl sulphoxide and acetic anhydride 493, 715). Because of the ease with which terphenylquinones themselves may be derived by methoxide catalysed rearrangement of grevilhns 462)... 

Maass, W. S. G., and A. C. Neish Lichen Substances II. Biosynthesis of Calycin and Pulvinic Dilactone by the Lichen, Pseudocyphellaria crocata. Canad. J. Botany 45, 59 (1967). 

Raghava Raju K, Rao PS (1985) Chemistry of Lichen Products. Part I. - Reaction of Hydrazine with Pulvinic Dilactone. Indian J Chem 24B 785... 

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... 

Polyporic acid (1) is converted in 95 % yield into pulvinic acid dilactone (2) on... 

Dilactones. Polyporic acid allowed to react 15 min. at 60° with a 1 2 mixture of acetic anhydride and dimethyl sulfoxide pulvinic acid dilactone. Y 90%. F. e. with monohydroxyquinones s. H. W. Moore and R. J. Wikholm, Tetrah. Let. 1968, 5049. 

Pulvinic acid dilactones from 2,5-dihydroxy-p-quinones... 

Other Activities. Picrolichenic acid was successfully used against intermittent fever (Alms 1832 Zopf 1907). Pulvinic acid dilactone has a pronounced cardiotonic activity (Nador et al. 1954), secalonic acid A has a phlogistic activity (Harada et al. 1974) and vulpinic acid an antiinflammatory activity (Foden et al. 1975). Usnic and diffractaic acids have analgesic and antipyretic activities comparable to amino-phenazone, phenylbutazone and hydrocortisone hemisuccinate (Dobrescu et al. 1993 Okuyama et al. 1995). 

Scheme 1.4 Pulvinic acid synthesis from dilactones 38 and azidoquinone 41.

Nuclear methoxylation occurs during the one-step photoconversion of pulvinic acid dilactone (206) into p-methoxyvulpinic acid (207) (Scheme 110). ... 

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