The stereocontrolled synthesis of the C（17）--C（28） fragment 3 of didemnaketal B was accomplished in 21 steps from the natural （R）-（＋）-pulegone and （S）-（--）-citronellal. The key steps involved diastereoselective construction of two chiral carbon centers through the intramolecular chiral induction and uncommon Julia olefination of ketone forming the E-trisubstituted C（22）--C（23） double bound.
＜正＞The genus Ligularia （Compositae） was made up of approximately 100 species and has extensive distribution. M...
WU, Quan-Xiang SHI, Yan-Ping (State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000) (Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000)
Two new butenolide derivatives, named as erigeracerin A and efigeracefin B, which are a pair of epimers, were isolated from Erigeron acer. Their structures were elucidated by spectroscopic analysis including 2D NMR and HR-ESI-MS.
The genus Gentiana (Gentianaceae) contains about 400 species, which distribute almost all over the world. Some species have been investigated on phytochemistry and they could be characterized by the presence of some secoiridoid glucosides (bitter principles), flavone-C-glucosides and xanthone aglycones and glucosides,[1] but nothing is known, up to now, about the chemical constitutents of Gentiana piasezkii Maxim. Members of the genus Gentiana have been used as traditional Chinese herbal medicines to treat hepatitis.[2] In order to find active compounds as lead molecule for medicine, we have studied on constituents of Gentiana piasezkii Maxim and found two new natural occurring,6'-O-(4-hydroxy-veratroyloxy)-arbutin (1) and luteolin 7-(3-hydroxy-4-methoxyl-cinnamoyl)-8-C-glucoside (2) from n-BuOH soluble fraction of an ethanolic extract of the whole plant. Their structures were elucidated by spectroscopic methods including 2D NMR techniques (1H-1H COSY, HMQC and HMBC). So we describe herein the structures of two new phenolic glucosides.……
