90
Coniferyl alcohol geranyl ether (979) was isolated from samples 8 and 10 and its
acetate 981 from samples 14 and 16. Interestingly, furanoeremophil-9-ene (270)
was isolated from sample 15, although most of the constituents were found have a
double bond at C-1/C-10 [31]. An intriguing phytochemical contribution appeared
in 2005 describing the isolation of only the lignans 1038 and 1042, with no terpenoids being reported at all (sample 18) [273]. Sample 19 produced a hydroperoxide
(21) and four triterpenoids (828 and 831–833) [56, 57]. The original report describing the isolation of 6α-hydroxyeremophil-7(11)-en-12,8β-olide cited an erroneous
paper. However, the
13
C NMR resonances attributed to C-6 and C-8 appeared at δ
34.9 and δ 104.3 ppm, respectively; with both of these chemical shift values indicating that the compound was actually 8-hydroxyeremophil-7(11)-en-12,8-olide. After
looking for a substitute candidate, compound 357 from L. vellerea was found to
have the same spectroscopic data. Therefore, compound 357 is listed in Table 9.
Isolation of a hydroperoxide from Ligularia, such as 21, is rather rare. Although a
hydroperoxide proton (-OOH) of 21 was reported in neither Refs [56] nor [57], it
was observed at δ 8.59 ppm (s) in the
1
H NMR spectrum published in Ref. [291].
The corresponding 11-hydroxy compound also is known [292]. This species usually
Fig. 21 10H-Eremophilan-12,8-olides (1)
M. Tori and C. Kuroda
Coniferyl alcohol geranyl ether (979) was isolated from samples 8 and 10 and its
acetate 981 from samples 14 and 16. Interestingly, furanoeremophil-9-ene (270)
was isolated from sample 15, although most of the constituents were found have a
double bond at C-1/C-10 [31]. An intriguing phytochemical contribution appeared
in 2005 describing the isolation of only the lignans 1038 and 1042, with no terpenoids being reported at all (sample 18) [273]. Sample 19 produced a hydroperoxide
(21) and four triterpenoids (828 and 831–833) [56, 57]. The original report describing the isolation of 6α-hydroxyeremophil-7(11)-en-12,8β-olide cited an erroneous
paper. However, the
13
C NMR resonances attributed to C-6 and C-8 appeared at δ
34.9 and δ 104.3 ppm, respectively; with both of these chemical shift values indicating that the compound was actually 8-hydroxyeremophil-7(11)-en-12,8-olide. After
looking for a substitute candidate, compound 357 from L. vellerea was found to
have the same spectroscopic data. Therefore, compound 357 is listed in Table 9.
Isolation of a hydroperoxide from Ligularia, such as 21, is rather rare. Although a
hydroperoxide proton (-OOH) of 21 was reported in neither Refs [56] nor [57], it
was observed at δ 8.59 ppm (s) in the
1
H NMR spectrum published in Ref. [291].
The corresponding 11-hydroxy compound also is known [292]. This species usually
Fig. 21 10H-Eremophilan-12,8-olides (1)
M. Tori and C. Kuroda