- A practical synthesis of β-D-mannopyranosides
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An indirect yet highly efficient protocol for the β-D-mannosylation of sterically hindered alcohols is reported. Trichloroacetimidate 5 is used a key building block which is converted into the desired mannosides 9 via triflates 8 by an ultrasound promoted
- Fuerstner, Alois,Konetzki, Ingo
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- Synthesis and biological evaluation of Raddeanin A, a triterpene saponin isolated from Anemone raddeana
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First, Raddeanin A, a cytotoxic oleanane-type triterpenoid saponin isolated from Anemone raddeana REGEL, was synthesized. Stepwise glycosylation was adopted in the synthesis from oleanolic acid, employing arabinosyl, glucosyl and rhamnosyl trichloroacetimidate as donors. The chemical structure of Raddeanin A was confirmed by means of 1H-NMR, 13C-NMR, IR, MS and elemental analysis, which elucidated the structure to be 3-O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranosyl-(1→2)-α-L-arabinopyranoside oleanolic acid. Biological activity tests showed that in the range of low concentrations, Raddeanin A displayed moderate inhibitory activity against histone deacetylases (HDACs), indicating that the HDACs' inhibitory activity of Raddeanin A may contribute to its cytotoxicity.
- Qian, Shan,Chen, Quan Long,Guan, Jin Long,Wu, Yong,Wang, Zhou Yu
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p. 779 - 785
(2016/10/12)
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- Total synthesis and absolute configuration of epicoccamide D, a naturally occurring mannosylated 3-acyltetramic acid
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The endofungal metabolite epicoccamide D was synthesised in eighteen steps and 17 % yield as the first member of the family of natural glycotetramic acids. The modular character of the synthesis opens access also to analogues featuring different sugars and spacers. It comprises several high-yielding key steps. The β-D-mannosyl group was introduced by using an α-D-glucosyl imidate donor with subsequent oxidative-reductive epimerisation at C-2′. The pyrrolidine ring was closed quantitatively by a Lacey-Dieckmann condensation of an N-(β-ketoacyl)-N-methyl alaninate. The resulting 3-[ω-(β-D- mannosyl)octadec-2-enoyl]tetramic acid was hydrogenated in the presence of the rhodium catalyst (R,R)-[Rh(Et-DUPHOS)][BF4] to establish the (7S)-stereocentre. This was possible only after blocking the acyltetramic acid as a BF2-chelate to prevent capture of the metal catalyst. We also assigned the hitherto unknown configuration of the natural product as being 5S,7S by comparison of its 13C NMR spectroscopic and optical rotation data with those of our two synthetic 5S,7R/S-diasteromers. Copyright
- Loscher, Sebastian,Schobert, Rainer
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p. 10619 - 10624
(2013/08/23)
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- Synthesis of 3-O-(β-d-xylopyranosyl-(1→2)-β-d-glucopyranosyl)-3′-O-(β-d-glucopyranosyl)tamarixetin, the putative structure of aescuflavoside A from the seeds of Aesculus chinensis
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3-O-(β-d-Xylopyranosyl-(1→2)-β-d-glucopyranosyl)-3′-O-(β-d-glucopyranosyl)tamarixetin, the putative flavonal glycoside named aescuflavoside A, isolated from the seeds of Aesculus chinensis, is synthesized via regioselective glycosylation of 7-O-benzyltama
- Zhu, Cunsheng,Peng, Wenjie,Li, Yuwen,Han, Xiuwen,Yu, Biao
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p. 1047 - 1051
(2007/10/03)
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- Efficient and direct synthesis of saccharidic 1,2-ethylidenes, orthoesters, and glycals from peracetylated sugars via the in situ generation of glycosyl iodides with I2/Et3SiH
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Peracetylated sugars can be efficiently converted into the corresponding 1,2-ethylidenes, -orthoesters, and -glycals via the in situ generation of glycosyl iodides promoted by I2/Et3SiH. The approach is straightforward and avoids isolation of the sensitive iodinated intermediates.
- Adinolfi, Matteo,Iadonisi, Alfonso,Ravidà, Alessandra,Schiattarella, Marialuisa
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p. 7863 - 7866
(2007/10/03)
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- ONE-POT SYNTHESIS OF SUBSTITUTED ALLYL-α-D-GLUCOPYRANOSIDES BY AN in situ ANOMERIZATION PROTOCOL
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A new 3-step, 1-pot procedure for the stereoselective α-glycosylation of substituted allylic alcohols has been developed.The key step involves an in situ anomerization of the β-glycoside, obtained by Schmidt's glycosylation method, upon treatment with TiCl4.
- Charette, Andre B.,Turcotte, Nathalie,Cote, Bernard
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p. 421 - 432
(2007/10/02)
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- 2-O-ACETYL-3,4-DI-O-BENZYL-6-O-(tert-BUTYLDIPHENYLSILYL)-D-GLUCOPYRANOSYL CHLORIDE AS A d-GLYCOSYL DONOR
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2-O-acetyl-3,4-di-O-benzyl-6-O-(tert-butyldiphenylsilyl-D-glucopyranosyl chloride, prepared from 6-O-(tert-butyldiphenylsilyl)1,2-O-(1-ethoxyethylidene)-α-D-glucopyranose in two steps, was treated separately with allyl alcohol, cyclohexanol, and benzyl 2-
- Sadeh, Shoshana,Warren Christopher D.,Jeanloz, Roger W.
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