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Iridoid glycosides from Callicarpa
Friday, April 9, 2010 -
New iridoid glycosides from the twigs and leaves of Callicarpa formosana var. formosana
Yu-Mei Wang, Huai Xiao, Ji-Kai Liu, Fei Wang*
J. Asian Nat. Prod. Res., 2010, 12(3): 220-226
Four new iridoid glycosides, 6-O-benzoylphlorigidoside B (1), 6-O-trans-cinnamoylphlorigidoside B (2), 6-O-trans-p-coumaroylshanzhiside methyl ester (3), and 4'-O-trans-p-coumaroylmussaenoside (4), were isolated from the EtOH extract of the twigs and leaves of Callicarpa formosana var. formosana. Their structures were elucidated by extensive spectroscopic analysis.
In the process of purification of 3, a 15% cis-p-coumaroyl isomer was concomitant with the goal all the while, and then preparative HPLC (15% MeCN in H2O, 10 mL/min) was applied to further isolate the isomers to afford 3 (tR=12.5 min; UV: 230, 314 nm) and its cis-isomer (tR=10.2 min; UV: 230, 307 nm), however, the pair of isomers were already inter-transformed in subsequent HPLC analysis.
Gernerally, the configuration (trans or cis) of cinnamoyl in most of cinnamoyl-containing molecules is inter-transformable in solvent, while cis-form always performs as a minor proportion from ~1% to ~20%.
Notes
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JCR 2010 --- Natural Product Chemistry
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