Lichens Lobaria retigera

The structure of retigeradiol, from the lichen Lobaria retigera, has been revised to stictane-3j8,22a-diol (211). It was originally thought to be taraxerane-3/3,19/3-diol. The ketol previously isolated from Centraria nivalis is probably 22a-hydroxystictan-3-one (212). ... 

Retigeranic acid, a sesterterpenoid from the lichen Lobaria retigera, was separated by HPLC into two stereoisomers, retigeranic acid A (551) and retigeranic acid B (552) the structures of both components were determined by X-ray analysis (675). 

In 1965 Seshardri et al. described the isolation of an unknown terpenoid acid B obtained from the lichens of Lobaria retigera in the western Himalayas [8]. (Note that this annotation bears no relation to the subsequent nomenclature later defined by Corey and Shibata.) Four collections had been made in the summer of 1962 from under the Rutba plants in the Valley of Flowers (12,500 feet) and on the way to Hemkund Lokpal (13,500 feet) and from underneath rocks and from pine trees in Ganghariya (10,000 feet). The samples were subjected to a series of increasingly polar extractions (petroleum ether, diethyl ether, acetone). The unknown terpenoid acid B was present in all petroleum ether extracts, except that of the sample obtained from the Valley of Flowers, in compositions ranging from 0.47 % to... 

Various fernanes are reported as constituents of some ferns, e.g. (+)-7- and (-)-8-femene as well as (-)-7,9(ll)-femadiene from Adiantum monochlamys and A pedatum (Pteridaceae). Hydroxylated derivatives are found in lichens such as reti-geric acid A in Lobaria retigera (Sticataceae) and some higher plants, e.g. (-)-7-femen-3p-ol in Rhododendron linearifolium (Ericaceae) and (-)-3p,lip-dihydroxy-8-femen-7-one in Euphorbia supina (Euphorbiaceae). 

Kaneda M, Takahashi R, litaka Y, Shibata S (1972) Retigeranic acid, a novel sesterterpene isolated from the lichens of Lobaria retigera group. Tetrahedron Lett 4609-4611... 

Takahashi R, Chiang H-C, Aimi N, Tanaka O, Shibata S (1972a) The structures of retigeric acids A and B from lichens of the Lobaria retigera group. Phytochetnistry 11 2039-2045... 

Retigeranic acid (480), isolated from the Lobaria retigera and related species, is the first example of a lichen sesterterpene. As sufficient information could not be obtained from routine spectral data 205), the structure (and absolute configuration) of (480) was determined by X-ray diffraction of the / -bromoanilide derivative of retigeranic acid 204). A possible biosynthetic route to (480) has also been outlined 205). 

Two fern-9(l l)-ene derivatives, retigeric acid A (496) and retigeric acid B (497), have been isolated from lichens of the Lobaria retigera group 313). The structures were deduced from H-n.m.r. and mass spectral properties of the acids and derivatives and were confirmed by X-ray analysis of / -bromophenacyl retigerate A 314). 

Takahashi, R., H.-C. Chiang, N. Aimi, O. Tanaka, and S. Shibata The Structures of Retigeric Acids A and B from Lichens of the Lobaria retigera Group. Phytochem. 11, 2039 (1972). 

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