95
in Fig. 31 [145]. The configurations of H-11 of compounds 544 and 545 also were
determined unambiguously [145]. Compound 328 is an enol form of a 9-one compound. Sample 3 from Shanxi Province, China, afforded the 10H-furanoeremophilane
212, three eremophilenolides (491–493), and two 15-oic acids (372 and 375) [141].
From sample 4 collected in Henan Province, China, isoligularonic acid (334) was
isolated [176]. This compound has a rearranged furan unit from the C-8 to the C-6
positions. Eighteen constituents were isolated from sample 5 by Bohlmann and
Knoll [20]. These comprised five bicyclic eremophilanes (1, 5, 6, 11, and 12), three
noreremophilanes (119, 121 (2-hydroxyplatyphyllide; “8-hydroxy” in the numbering of the original report), and 125), four 1,10-epoxides (290, 291, 293, and 295 (the
major constituent)), and four aromatic compounds (940, 944, 952, and 954) [20].
Although the (S)-(+)-form for hydroxytremetone (940) was shown without appropriate detail in Ref. [20], the absolute configuration of natural (−)-940 was determined to be (R), by transformation and degradation of this substance into a known
chiral compound [293].
Fig. 25 10-OH-Eremophila-7(11),8-dien-12,8-olides
Chemical Constituents of Ligularia Species (Asteraceae) and Their Diversity…
in Fig. 31 [145]. The configurations of H-11 of compounds 544 and 545 also were
determined unambiguously [145]. Compound 328 is an enol form of a 9-one compound. Sample 3 from Shanxi Province, China, afforded the 10H-furanoeremophilane
212, three eremophilenolides (491–493), and two 15-oic acids (372 and 375) [141].
From sample 4 collected in Henan Province, China, isoligularonic acid (334) was
isolated [176]. This compound has a rearranged furan unit from the C-8 to the C-6
positions. Eighteen constituents were isolated from sample 5 by Bohlmann and
Knoll [20]. These comprised five bicyclic eremophilanes (1, 5, 6, 11, and 12), three
noreremophilanes (119, 121 (2-hydroxyplatyphyllide; “8-hydroxy” in the numbering of the original report), and 125), four 1,10-epoxides (290, 291, 293, and 295 (the
major constituent)), and four aromatic compounds (940, 944, 952, and 954) [20].
Although the (S)-(+)-form for hydroxytremetone (940) was shown without appropriate detail in Ref. [20], the absolute configuration of natural (−)-940 was determined to be (R), by transformation and degradation of this substance into a known
chiral compound [293].
Fig. 25 10-OH-Eremophila-7(11),8-dien-12,8-olides
Chemical Constituents of Ligularia Species (Asteraceae) and Their Diversity…