200424-82-4Relevant articles and documents
InBr 3 -Catalyzed Synthesis of Aryl 1,2- trans -Thio(seleno)glycosides
Ma, Teng,Li, Changwei,Liang, Haijing,Wang, Zhaoyan,Yu, Lan,Xue, Weihua
supporting information, p. 2311 - 2314 (2017/10/06)
InBr 3 is demonstrated to be an efficient catalyst for reactions of fully acetated aldoses with aryl mercaptans or selenophenol at room temperature, rapidly furnishing the corresponding thioglycosides or selenoglycosides with exclusively 1,2- t
Highly α- and β-selective radical C-glycosylation reactions using a controlling anomeric effect based on the conformational restriction strategy. A study on the conformation - Anomeric effect - Stereoselectivity relationship in anomeric radical reactions
Abe,Shuto,Matsuda
, p. 11870 - 11882 (2007/10/03)
We hypothesized that, because the stereoselectivity of anomeric radical reactions was significantly influenced by the anomeric effect, which can be controlled by restricting the conformation of the radical intermediate, the proper conformational restriction of the pyranose ring of the substrates would therefore make highly α- and β-stereoselective anomeric radical reactions possible. Thus, the conformationally restricted 1-phenylseleno-D-xylose derivatives 9 and 10, restricted in a 4C1-conformation, and 11 and 12, restricted in a 1C4-conformation, were designed and synthesized by introducing the proper protecting groups on the hydroxyl groups on the pyranose ring as model substrates for the anomeric radical reactions. The radical deuterations with Bu3SnD and the C-glycosylation with Bu3SnCH2CH=CH2 or CH2=CHCN, using the 4C1-restricted substrates 9 and 10, afforded the corresponding α-products (α/β = 97:3-85:15) highly stereoselectively, whereas the 1C4-restricted substrates 11 and 12 selectively gave the β-products (α/β = 1:99-0:100). Thus, stereoselectivity was significantly increased by conformational restriction and was completely inverted by changing the substrate conformation from the 4C1-form into the 1C4-form. Ab initio calculations suggested that the radical intermediates produced from these substrates possessed the typical 4C1- or 1C4-conformation, which was similar to that of the substrates, and that the anomeric effect in these conformations would be the factor controlling the transition state of the reaction. Therefore, the highly α- and β-selective reactions would occur because of the anomeric effect, which could be manipulated by conformational restriction of the substrates, as expected. This would be the first radical C-glycosylation reaction to provide both α- and β-C-glycosides highly stereoselectively.
Total synthesis of everninomicin 13,384-1 - Part 2: Synthesis of the FGHA2 fragment
Nicolaou,Mitchell, Helen J.,Fylaktakidou, Konstantina C.,Rodriguez, Rosa Maria,Suzuki, Hideo
, p. 3116 - 3148 (2007/10/03)
The stereoselective synthesis of everninomicin's 13,384-1 (1) FGHA2 fragment (2) in a suitable form for incorporation into the final target (1) is described. The construction of the FG 1,1′-disaccharide linkage relied on a new method based on tin-acetal chemistry, while for the GH orthoester bridge, a number of approaches were explored. Final success for the latter construction came when a novel 1,2-phenylseleno migration reaction was applied to couple rings G and H, followed by ketene acetal and orthoester formation.
