Synthesis of peracetylated C-1-deoxyalditol- and C-glycoside-dipyrranes via dithioacetal derivatives
作者:Stephanie M.S. Ló、Juliana C. Cunico、Diogo R.B. Ducatti、Alexandre Orsato、M. Eugênia R. Duarte、Sandra M.W. Barreira、Miguel D. Noseda、Alan G. Gonçalves
DOI:10.1016/j.tetlet.2012.12.048
日期:2013.2
Dipyrranes bearing peracetylated mono- or disaccharidic C-1-deoxyalditol moieties were prepared from D-galactose, c-glucose, c-mannose, and lactose. A partially hydrolyzed polysaccharide (agarose) was also used as starting material for the synthesis of a disaccharide-containing C-glycoside dipyrrane. These compounds were synthesized as follows: the sugar starting materials were first submitted to a mercaptolysis-acetylation one-pot procedure (EtSH/HCl-Ac2O/pyridine). The resulting peracetylated diethyl dithioacetals were converted into dipyrranes through carbonyl deprotection (H5IO6, THF-Et2O) followed by TFA-catalyzed pyrrole condensation with yields up to 62%. Overall yields from sugar starting materials were up to 49%. (C) 2012 Published by Elsevier Ltd.
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
Studies on the Chemical Constitution of Agar-agar. XVI. Isolation of Crystalline Agarobiose Diethylmercaptal by Mercaptolysis of Agar-agar