147
C-6. The 4α-substituted carboxy group present in compound 373 is of considerable interest.
Our research team has made a preliminary communication on the isolation of
three lactones (522, 544, and 545) from sample 3 (from Gansu Province) [145].
Eremopetasitenin B4 (522) and eremofarfugins F (545) and G (544) were assigned
as epoxy- and enol-lactones, respectively. In 1997, Chen et al. reported compound
522 from L. intermedia, and this was assigned as having a 7α,8α-epoxide functionality [140]. However, we have revised the structure of this compound unambiguously as a 7β,8β-epoxide using NOE experiments and by X-ray diffraction analysis
[145]. The stereochemistry of both epoxide at C-7/C-8 and the methyl group at C-11
may be difficult to determine in the structure determination of this type of sesquiterpenoid. A decisive NOE effect cannot always be observed, and thus the relative
configurations of some compounds have been left undetermined [300]. We proposed plausible biosynthesis pathways, which supported the above results. At the
same time, the configuration at C-11 of both compounds 544 and 545 was determined [145].
Two triterpenoid glycosides (861 and 862) were isolated from sample 4 (Qinghai
Province, China) [252]. No terpenoids were found in sample 4. Sample 5 (Anhui
Province, China) produced six bicyclic compounds (41, 67, 69, 70, 110, and 124),
and an eremophilatrienolide (449; major constituent) [64]. Sample 6 (Gansu
Province, China) produced four bicyclic compounds (43, 119, 121, and 134), seven
eremophilanolides (372, 490, 491, 493, 509, 511, and 513), and six aromatic derivatives (902, 941, 951, 952, 957, and 1011) [70, 265]. Five eremophilanolides (372,
490, 491, 493, and 509) and five aromatics (952, 954, 957, 960, and 964) were isolated from sample 7 (Gansu Province) [189].
Fig. 66 Aromatic compounds (5)
Chemical Constituents of Ligularia Species (Asteraceae) and Their Diversity…
C-6. The 4α-substituted carboxy group present in compound 373 is of considerable interest.
Our research team has made a preliminary communication on the isolation of
three lactones (522, 544, and 545) from sample 3 (from Gansu Province) [145].
Eremopetasitenin B4 (522) and eremofarfugins F (545) and G (544) were assigned
as epoxy- and enol-lactones, respectively. In 1997, Chen et al. reported compound
522 from L. intermedia, and this was assigned as having a 7α,8α-epoxide functionality [140]. However, we have revised the structure of this compound unambiguously as a 7β,8β-epoxide using NOE experiments and by X-ray diffraction analysis
[145]. The stereochemistry of both epoxide at C-7/C-8 and the methyl group at C-11
may be difficult to determine in the structure determination of this type of sesquiterpenoid. A decisive NOE effect cannot always be observed, and thus the relative
configurations of some compounds have been left undetermined [300]. We proposed plausible biosynthesis pathways, which supported the above results. At the
same time, the configuration at C-11 of both compounds 544 and 545 was determined [145].
Two triterpenoid glycosides (861 and 862) were isolated from sample 4 (Qinghai
Province, China) [252]. No terpenoids were found in sample 4. Sample 5 (Anhui
Province, China) produced six bicyclic compounds (41, 67, 69, 70, 110, and 124),
and an eremophilatrienolide (449; major constituent) [64]. Sample 6 (Gansu
Province, China) produced four bicyclic compounds (43, 119, 121, and 134), seven
eremophilanolides (372, 490, 491, 493, 509, 511, and 513), and six aromatic derivatives (902, 941, 951, 952, 957, and 1011) [70, 265]. Five eremophilanolides (372,
490, 491, 493, and 509) and five aromatics (952, 954, 957, 960, and 964) were isolated from sample 7 (Gansu Province) [189].
Fig. 66 Aromatic compounds (5)
Chemical Constituents of Ligularia Species (Asteraceae) and Their Diversity…