Phytochemistry, Vol. 21, No. 12, pp. 2899-2903, 1982. Printed in Great Britain. 0031-9422/82/122899-05$03.00/O 0 1982 Pergamon Press Ltd. zyxwvut FURANOHELIANGOLIDES AND FARNESOL DERIVATIVES FROM CALEA HISPIDA” FERDINAND BOHLMANN, RAJINDER K. GUPTA, JASMIN JAKUPOVIC, ROBERT M. KINGt and HAROLD RoBINsoNt Institute for Organic Chemistry, Technical University of Berlin, D-1000 Berlin 12, West Germany; tSmithsonian Institution, Department of Botany, Stop No. 166, Washington, DC 20560, U.S.A. (Revised received 5 March 1982) Key Word Index-Calea hispida ; Compositae; sesquiterpene lactones; furanoheliangolides; myrtenyl substituted sesquiterpene lactone; farnesol derivatives; dihydroxy dehydromenthone. Abstract-From Calea hispida, in addition to known compounds, two new furanoheliangolides, one substituted with a myrtenyl residue, two further farnesol derivatives and a dihydroxy dehydromenthone were isolated. The structures were elucidated by high field ‘H NMR spectroscopy and by comparison of the data with those of similar compounds. The chemotaxonomic situation is discussed briefly. INTRODUCTION Several species of the large genus Calea (tribe Heli- antheae) with ca 100 taxa have already been in- vestigated chemically. Most of them afforded sesqui- terpene lactones, especially furanoheliangolides [l-8], but also other germacranolides [l, 2,4,9-121 and a few eudesmanolides [4,71 were found. Furthermore, several species gave prenylated p-hydroxy- acetophenone derivatives [3,5-7,13,14]. We now have studied the constituents of Calea hispida (DC.) Baker. The results are discussed in this paper. RESULTSAND DISCUSSION The roots of C. hispida afforded the thymol derivatives l-4, the eudesmene derivative 9 [15] and the chromenes 5-8 [ 16-181, while the aerial parts gave germacrene D, caryopyhllene, a-humulene, bicyclo- germacrene, 2, 4, the furanoheliangolides 12 [3] and 13 [l], the heliangolide 11 [19], two further helian- golides, the myrtenyl substituted angelate 14 and the hydrated furanoheliangolide 15, the farnesol deriva- tives 16 and 17 as well as the dihydroxy dehy- dromenthone 10. The structure of the latter followed from the molecular formula and the ‘H NMR spectral data (see Experimental). Spin decoupling showed that the isopropyl proton was allylic to the olefinic proton. The chemical shift of the latter showed that it must be in a P-position to the keto group. The presence of an unsaturated keto group also was evident from the corresponding IR band (1690 cm-‘). The olefinic pro- ton was further coupled with a proton, which dis- played a double doublet at S 4.30. The latter was further coupled with a hydroxy doublet at 8 2.41. *Part 453 in the series “Naturally Occurring Terpene Derivatives”. For Part 452 see Bohlmann, F. and Zdero, C. (1982) Phytochemistry 21, 2263. Accordingly, the sequence A was established. OH , CH Me, .-fi=Cyo zyxwvutsrqponmlkjihgfedcbaZYXWVUTSR A A downfield methyl singlet at 6 1.36 indicated the presence of a tertiary hydroxyl group, while a pair of doublets at 6 2.74 and 2.50 obviously were the signals of a methylene group a to the carbonyl. Thus the structure of 10 was established, but the stereoche- mistry at C-l could not be determined. Probably 10 was formed by hydroxylation of 1,2,3,4-tetradehy- dromenthone, an intermediate in the biogenesis of thymol. The diacetate 16 gave no molecular ion in the mass spectrum, similarly chemical ionization produced an ion by loss of acetic acid. The ‘H NMR spectrum, however, showed (Table 1) that a diacetate was present. A three-fold doublet at 8 4.49 indicated an additional hydroxyl group. Spin decoupling showed that the corresponding proton was coupled with an olefinic proton, which displayed a broadened double quartet at 8 5.19. Further couplings with two pairs of double doublets at 8 2.45 and 2.24 showed that the allylic hydroxyl group was at C-S or C-9 of a farnesol with an acetoxyl group at C-15. The position of the latter followed from the chemical shifts of the olefinic protons and methyl groups. Spin decoupling further indicated that the broadened triplet at 6 5.06 showed allylic couplings with two olefinic methyls. Accordingly, the hydroxyl group was at C-5. In addition 17 showed no molecular ion in the mass spectrum even under CI conditions where, however,