From <i>α</i>‐1,2‐Anhydrosugars to <i>C</i>‐Glycosides: The Influence of Lewis Acids and Nucleophiles on the Stereochemistry
作者:Michiel A. Leeuwenburgh、Gijsbert A. van der Marel、Herman S. Overkleeft、Jacques H. van Boom
DOI:10.1081/car-120026458
日期:2003.12.31
Ring opening of the epoxide function in alpha-1,2-anhydrosugars with alkynyl zinc and titanium compounds proceeds with retention of configuration to afford alpha-C-alkynylglycosides in reasonable to good yields, while the use of the corresponding alkynyltrifluoroborates results in the formation alpha/beta mixtures. Vinyl nucleophiles predominantly afford alpha-products, whereas allyl and allenyl species almost exclusively yield beta-C-glycosides.
Stereoselective Synthesis of α-C-(alkynyl)-glycosides via Ring-opening of α-1,2-Anhydrosugars
作者:Michiel A Leeuwenburgh、Cornelis M Timmers、Gijsbert A van der Marel、Jacques H van Boom、Jean-Maurice Mallet、Pierre G Sinaÿ
Zinc-Mediated Synthesis of α-<i>C</i>-Glycosides from 1,2-Anhydroglycosides
作者:Song Xue、Kai-Zhen Han、Lin He、Qing-Xiang Guo
DOI:10.1055/s-2003-38751
日期:——
α-C-Glycosides have been prepared by the addition of organozinc reagents to glycal epoxides. Dialkyl and diaryl zinc reagents in the presence of CF3COOH provide the corresponding α-glycosides in 53-82% yields. Organozinc chlorides RZnCl formed by the reaction RLi with zinc chloride can also be successfully applied to this coupling reaction with high α-selectivity.