Cheng Lijian, Chen Qi, Du Yuguo
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Carbohydr Res. 2007 Aug 13;342(11):1496-501. doi: 10.1016/j.carres.2007.05.019. Epub 2007 May 18.
A tetrasaccharide, dodecanyl 4-O-acetyl-alpha-l-rhamnopyranosyl-(1-->3)-2,4-di-O-acetyl-alpha-l-rhamnopyranosyl-(1-->3)-4-O-acetyl-alpha-l-rhamnopyranosyl-(1-->4)-alpha-l-rhamnopyranoside (cleistetroside-2), was synthesized via '2+2' convergent strategy. Sequential regioselective 3-O-glycosylation of isopropyl 1-thio-alpha-l-rhamnopyranoside (4) with 4-O-acetyl-2,3-O-isopropylidene-alpha-l-rhamnopyranosyl trichloroacetimidate (8), and isopropyl 4-O-acetyl-2,3-O-isopropylidene-alpha-l-rhamnopyranosyl-(1-->3)-2,4-di-O-acetyl-alpha-l-1-thio-rhamnopyranoside (10) with dodecanyl 4-O-acetyl-alpha-l-rhamnopyranosyl-(1-->4)-2,3-O-isopropylidene-alpha-l-rhamnopyranoside (12), greatly facilitate the target availability.
通过“2+2”汇聚策略合成了一种四糖，十二烷基4-O-乙酰基-α-L-鼠李吡喃糖基-(1→3)-2,4-二-O-乙酰基-α-L-鼠李吡喃糖基-(1→3)-4-O-乙酰基-α-L-鼠李吡喃糖基-(1→4)-α-L-鼠李吡喃糖苷（裂叶金丝桃苷-2）。1-硫代-α-L-鼠李吡喃糖苷异丙酯（4）与4-O-乙酰基-2,3-O-亚异丙基-α-L-鼠李吡喃糖基三氯乙酰亚胺酯（8）进行顺序区域选择性3-O-糖基化反应，以及4-O-乙酰基-2,3-O-亚异丙基-α-L-鼠李吡喃糖基-(1→3)-2,4-二-O-乙酰基-α-L-1-硫代鼠李吡喃糖苷（10）与十二烷基4-O-乙酰基-α-L-鼠李吡喃糖基-(1→4)-2,3-O-亚异丙基-α-L-鼠李吡喃糖苷（12）进行反应，极大地促进了目标产物的合成。
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