Carlina oxide

Cinnamic acid Natural balsam, cocoa leaves, cinnamol oil Carlina oxide Carline aeaulis L. 

Furans are occasionally found in plants and microorganisms, e.g. carlina oxide 26, which is obtained by steam distillation from the roots of the carline thistle Carlina acaulis) ... 

Caffeine 478, 479 Camptothecin 405 Cannabinol 345 Cantharidin 89 Carazolol 149 l,l -Carbonyldiimidazol 228 Carlina oxide 78 Capri Blue 446 e-Caprolactam see azepan-2-one Captopril 161 Carbamazepine 539 Carbazole 148, 149 Carbostyryl 387 Cardiazol see pentetrazole Catechin 340 Cefatrizin 264 Celecoxib 243 Cephalosporin 455 Cepham 455 Cerivastin 379 Chalciporon 539 Chelidonic acid 335 Chemiluminescence 55 1-Chlorobenzotriazole 267 Chlordiazepoxide 544 Chlorin 551... 

The oil has been, however, carefully investigated by Semmler. It contains about 15 per cent, of a monocyclic sesquiterpene, Cx5Hj, boiling at IdO at 20 mm., and of specific gravity 0-8733 and refractive index 1-4920. An oxide, termed Carlina oxide, C jO, of specific gravity 1-066 and refractive index 1-5860, forms the principal constituent of the oil. It is a complex furane derivative of the constitution. CH -. C CH. (C HjO). Semmler has also isolated a sesquiterpene which... 

No other natural compounds were recognized as acetylenes until 1933 > when the correct structure (II) for carlina oxide (isolated in 1906 by Semmler) was proposed (Gilman van Ess and Burtner, 1933). 

The furane ring was reported in one of the earhest described acetylenic compounds, carlina oxide (II). The formal relationship between (II) and the alcohol (LIV) isolated (as the acetate) from Coreopsis species (Sorensen and Sorensen, 1954) was pointed out by Jones and Whiting (quoted in Sorensen and Sorensen, 1954). 

The biological production of the furane ring from an enynic alcohol was demonstrated by Bohlmann and v. Kap-herr (1966). When the alcohol LXXXII, labelled with tritium in the benzene ring was injected into the root of Carlina acauUs, the carlina oxide (II) isolated was labelled and all of its tritium was in the benzene ring. 

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