Regio- and stereoselective anomeric esterification of glucopyranose 1,2-diols and a facile preparation of 2-O-acetylated glucopyranosyl trichloroacetimidates from the corresponding 1,2-diols

Abstract

Abstract-A highly regio-and stereoselective anomeric esterification of 3-O-allyl (or benzyl, or benzoyl)-4,6-O-isopropylidene-a,b-D D-glucopyranose with acetyl chloride, or allyl chloroformate, or ethyl chloroformate gave the corresponding 2-OH, 1-b-acetates or -carbonates in excellent yields. The 2-OH, 1-b-acetates were readily converted to the corresponding 2-O-acetylated glucopyranosyl trichloroacetimidates by reaction with trichloroacetonitrile via base promoted acetyl migration, while the 2-OH, 1-b-carbonates were good glycosyl acceptors for the synthesis of (1!2)-linked oligosaccharides.

Synthesis and Anti-Fungal Activity of Seven Oleanolic Acid Glycosides

“…2,3,4,6-Tetra- O -benzoyl-β-D-galactopyranose-(1→3)-1,2- O -isopropylidene-β-D-xylose 28 was conveniently prepared from 25 in 70% overall yield, via selective removal of the 5,6- O -isopropylidene group followed by NaIO 4 oxidation and NaBH 4 reduction in a similar way as reported in [17]. Subsequently, hydrolysis of 28 was carried out in an aqueous solution of sulfuric acid (4%) under heating at reflux, and the reaction was accompanied by ring expansion [18] to provide 2,3,4,6-tetra– O -benzoyl-β-D-galactopyranose-(1→3)-β-D-xylose 29 , which was benzoylated with benzoyl chloride in pyridine. Regioselective removal of the 1- O -benzoyl group in 2 M MeOH-NH 3 followed by trichloroacetimidation with trichloroacetonitrile [9] afforded building block 15 in 68% yield (3 steps).…”

Új β-cukoraminosavak előállítása és beépítése foldamerekbe

“…(46), mint kiindulási anyagot állítjuk elő, amelyre van példa az irodalomban. [66][67][68] Ezek közül az egyik leggyakrabban alkalmazott módszer a D-arabinózból (47) kiinduló 5 lépéses szintézis (10. ábra). 66 Első lépése a D-arabinóz (47) nitrometános lánchosszabbítása, amely a megfelelő 1-dezoxi-1-nitro-D-glücitolt (48) és 1-dezoxi-1-nitro-D-mannitolt (49) eredményezi.…”

Efficient Synthesis of Allolactose

“…双羟基受体 6 与供体 3 在 TMSOTf 催化下进行偶联 反应 [13] , 期待在受体 线大量制备目标双糖的应用受到一定限制, 因此我们进 一步探索了异乳糖的逐步合成法. 之前在多个生物活性分子的合成中, 课题组探索了 酰基对羟基的选择性保护方法 [10,14,15] , 重点发展了烯丙 氧羰基作为寡糖合成的选择性正交保护基的脱除方 法 [16] , 并应用该方法完成了多个糖环羟基的选择性保护 以及多个复杂的重要生物活性的寡糖的首次合成 [17～20] . 该保护基在缓冲剂乙酸铵存在、四三苯基膦钯催化下, 可以在 5 min 内以硼氢化钠近似定量脱除而不影响分子 中其他众多基团, 尤其是酰基.…”