Production of carbohydrate building blocks from red seaweed polysaccharides. Efficient conversion of galactans into C-glycosyl aldehydes
作者:Diogo R. B. Ducatti、Alessandro Massi、Miguel D. Noseda、Maria Eugênia R. Duarte、Alessandro Dondoni
DOI:10.1039/b816606d
日期:——
and D-galactose, respectively) derivatives. Complete depolymerization of agarose and kappa-carrageenan under harsher conditions produced 3,6-anhydro L- and D-galactose aldehydederivatives. Chain shortening of these products via alditol formation and oxidative carbon-carbon bond cleavage furnished C-formyl α-L- and α-D-threofuranosides. The above C-glycosyl aldehydes were all prepared on a meaningful
琼脂和角叉菜胶是丰富的天然多糖,可通过以下方法大规模获得 水从各种红色海藻中提取。这些半乳聚糖,除了是制药和食品工业的有价值的产品外,还是低成本的原料,用于制备有用的和稀有的,基于碳水化合物的结构单元,这些单元很难通过全合成获得,而且价格昂贵。半合成L-和D-构象的两组C-糖基醛的半合成。琼脂糖分别描述了α-角叉菜胶和κ-角叉菜胶。简而言之,在温和条件下,两个半乳聚糖的部分酸催化巯基分解反应得到琼脂二糖 和角蛋白(β- d -Gal p - (1→4)-3,6-脱水-醛基-大号- 和 D-半乳糖)。完全解聚琼脂糖 和κ-角叉菜胶在更苛刻的条件下产生 3,6-脱水 L-和D-半乳糖醛衍生物。通过醛糖醇形成和氧化碳-碳键裂解提供的这些产品的链缩短C-甲酰基α- L-和α- D-呋喃呋喃糖苷。以上C-糖基醛均以克量的半乳聚糖为起始以有意义的制备规模制备。最终,通过Baeyer-Villiger氧化苄基化反应建立了一种新的制备2
Dihydropyridine C-glycoconjugates by organocatalytic Hantzsch cyclocondensation. Stereoselective synthesis of α-threofuranose C-nucleoside enantiomers
作者:Diogo R. B. Ducatti、Alessandro Massi、Miguel D. Noseda、Maria Eugênia R. Duarte、Alessandro Dondoni
DOI:10.1039/b900422j
日期:——
The Hantzsch reaction of C-glycosyl aldehyde/enamino ester/β-ketoester systems under L-proline catalysis to give dihydropyridineC-glycoconjugates is reported. Asymmetric cyclocondensations of differentially substituted enamine and β-dicarbonyl components with formyl α-L-C-threofuranoside and with the α-D-isomer were also carried out. Each reaction occurred with high yet opposite stereoselectivity (de
C-糖基醛/氨基酯/β-酮酸酯体系的Hantzsch反应。大号脯氨酸据报道催化产生二氢吡啶C-糖缀合物。还进行了不同取代的烯胺和β-二羰基组分与甲酰基α- L - C-苏糖呋喃糖苷和α- D-异构体的不对称环缩合。每个反应都以高但相反的立体选择性(de> 95%)发生,因此制备了一对α-苏呋喃糖C-核苷对映体。