Daniellou Richard, Palmer David R J
Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan, Canada S7N 5C9.
Carbohydr Res. 2006 Sep 4;341(12):2145-50. doi: 10.1016/j.carres.2006.05.001. Epub 2006 May 24.
We recently reported that inositol dehydrogenase (EC 1.1.1.18) from Bacillus subtilis can catalyze the highly stereoselective oxidation of 1l-4-O-substituted myo-inositol derivatives, as well as disaccharides melibiose and isomaltose, but not gentiobiose or maltose, consistent with the requirement of an alpha-(1-->6) linkage. We believed that the enzyme might therefore catalyze efficient stereoselective oxidation of the appropriate alpha-linked glycosyl inositols. We have synthesized alpha-D-glucopyranosyl-(1-->4)-(DL)-myo-inositol and alpha-d-galactopyranosyl-(1-->4)-(DL)-myo-inositol using the Appel-Lee protocol to couple benzyl-protected glycosyl donors to protected inositols. This method failed in our hands using glycosyl donors derived from D-mannose and 2-azido-2-deoxy-D-glucose. When myo-inositol 1,3,5-monoorthoformate is used as the acceptor, the reaction is regiospecific for the 4/6-position. We report here the mildest conditions known for the removal of the orthoformate group. 2-Azido-2-deoxy-alpha-D-glucopyranosyl-(1-->4)-(DL)-myo-inositol was synthesized using the trichloroacetimidate derivative as the donor, and all three pseudo-disaccharides were substrates for inositol dehydrogenase. The glucopyranosyl and galactopyranosyl derivatives displayed apparent second-order rate constants comparable to that of myo-inositol.
我们最近报道，来自枯草芽孢杆菌的肌醇脱氢酶（EC 1.1.1.18）可以催化1l-4-O-取代的肌醇衍生物以及二糖蜜二糖和异麦芽糖的高度立体选择性氧化，但不能催化龙胆二糖或麦芽糖的氧化，这与α-(1→6)键的要求一致。我们认为，因此该酶可能催化适当的α-连接糖基肌醇的高效立体选择性氧化。我们使用阿佩尔-李方法将苄基保护的糖基供体与保护的肌醇偶联，合成了α-D-吡喃葡萄糖基-(1→4)-(DL)-肌醇和α-D-吡喃半乳糖基-(1→4)-(DL)-肌醇。当使用D-甘露糖和2-叠氮基-2-脱氧-D-葡萄糖衍生的糖基供体时，这种方法在我们手中失败了。当肌醇1,3,5-单原甲酸酯用作受体时，反应对4/6位具有区域特异性。我们在此报告了已知的去除原甲酸酯基团的最温和条件。使用三氯乙酰亚胺衍生物作为供体合成了2-叠氮基-2-脱氧-α-D-吡喃葡萄糖基-(1→4)-(DL)-肌醇，所有三种假二糖都是肌醇脱氢酶的底物。吡喃葡萄糖基和吡喃半乳糖基衍生物的表观二级速率常数与肌醇的相当。
