P-Orcinol Depsidones

Protocetraric acid (424) has been synthesized by Sala and Sargent (277) by dibromination of the synthetic depsidone (420) and hydrolysis of the product. The resultant diol (421) was partially demethylated and converted into the acetonide (422), This on oxidation with pyridinium chlorochromate and deprotection gave the methyl 0-methylprotocetrarate (423) which on demethylation gave protocetraric acid (424). 

Succinprotocetraric acid, from Parmelia reptans and Chondropsis semi-viridis (77), and malonprotocetraric acid from Parmotrema conformatum (208), are derivatives of protocetraric acid (424) in which the benzyl alcohol 

Galbinic acid (432) from Usnea undulata is an acetyl derivative of salazinic acid (291) from which it can be prepared by heating it in acetic acid containing TVW-dimethylformamide (114). 

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P-Orcinol depsidones All lichen substances Aromatic aldehydes... 

Chem Unserer Zeit 16 71-88 II. ibid. 16 116-123 Keogh MF (1976) 2 -0-Demethylpsoromic acid from Us-nea sp. Phytochemistry 15 1801 Keogh MF (1977) Malonprotocetraric acid from Parm-otrema conformatum. Phytochemistry 16 1102 Keogh MF (1978) New P-orcinol depsidones from Xanthoparmelia quintaria and a Thelotrema species. Phytochemistry 17 1192-1193 Keogh MF, Duran I (1977) A new fatty acid from Usnea meridensis. Phytochemistry 16 1605-1606 Keogh MF, Zurita ME (1977) a-(15-Hydroxyhexadecyl) itaconic acid from Usnea aliphatica. Phytochemistry 16 134-135... 

Sala T, Sargent MV (1981) Depsidone synthesis. Part 19. Some P-orcinol depsidones. J Chem Soc Perkin Trans 1 877-882... 

Except in gangaleoidin, the A ring of all p-orcinol depsidones has either a 3-aldehydic substituent like the A ring of the para-depside atranorin or a... 

In the ten years since the last review there has been a resurgence of interest in the chemistry of depsidones in terms of the detection (79), the isolation of new compounds and the total synthesis of these substances. The new work is discussed in the order of the above classification and of increasing structural complexity of the compounds. A methodical study and interpretation of the C-n.m.r. spectra of orcinol 311) and P-orcinol depsidones 312) has been reported by Sundholm and Huneck. 

New p-Orcinol Depsidones from Xanthoparmelia quintaria and a Thelometra Species. Phytochem. 17, 1192 (1978). 

O Donovan, D. G., G. Roberts, and M. F. Keogh Structure of the P-Orcinol Depsidones, Connorstictic and Consalazinic Acids. Phytochem. 19, 2497 (1980). Ollis, W. D. Personal Communication. 

Elix JA, Lumbsch HT, Wardlaw JH (1995) Conhypoprotocetraric Acid, a New Lichen P-Orcinol Depsidone. Aust J Chem 48 1479... 

Sundholm EG, Huneck S (1981) C NMR-spectra of lichen depsides, depsidones and depsones. 2. Compounds of the P-orcinol series. Chem Scripta 18 233-236... 

The biogenetically simplest of the third class of depsidones, those in which one benzenoid ring is derived from orsellinic acid and one from P orcinol carboxylic acid, is nornotatic acid (293) (Scheme 55). T.l.c. evidence was presented by Culberson and Hale 82) for its occurrence in many lichens. They advanced structure (293) on the basis of the chromatographic... 

Phenylenediamine reacts with aromatic aldehydes, giving yellow to red Schiff bases (Fig. lb). Most -orcinol depsidones, as well as some -orcinol depsides, give a positive PD test. Aromatic diamines other than p-phenyl-enediamine also react with aromatic aldehydes. Asahina (1934) found that benzidin gives less intensely colored reaction products thanp-phenylenedia-mine. Santesson (1966) compared some diamine reagents and suggested the use of o-dianisidine (OD) as a PD substitue. o-Dianisidine is more sensitive, more stable, and more toxic than PD, but not as corrosive. The color reactions obtained with OD are not always identical with those of PD. 

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