Six new O-terpenoidal coumarins named excavacoumarins B-G (1-6) were isolated from the aerial part of Clausena excavata collected in Xishuangbanna, Yunnan.Clausena excavata Burm.f. (Rutaceae) is a bush widely distributed in Yunnan, China.Leaves and barks of this plant have been used as folk medicine for the treatment of dysentery，enteritis，and urethra infection. 1Previous researches revealed that this plant mainly contained alkaloids, 2-4 coumarins, 5-9 and flavonoid glycosides. 10This paper described the isolation and structure elucidation of six newOterpenoidal coumarins, excavacoumarins B-G (1-6) and one known coumarin (7). 5,9 molecular formulae of excavacoumarins B-G (1-6) were established by high-resolution EIMS analyses.The inspection of NMR data (proton, carbon, DEPT) (Table 1 and 2) revealed that compounds (1-6) had the same coumarin moieties and different 10-carbon side chains.The 1 H and 13 C NMR data for the coumarin moieties of 1-6 were similar with those of excavacoumarin A, 8 indicating their side chains linked to C-7 via an oxygen.The 13 C NMR signals at δ C 195.2 (s), 174.4 (s) and 161.1 (s), and the IR data (1728, 1750, 1755 cm -1 ) revealed three carbonyls in 1, suggesting a keto and lactone in the side chain.The proton signal at δ 5.61 (2H) appeared as a singlet, revealing the ketone (δ C 195.2)
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Hao et al. (2000) studied this question.