Synthesis of the Fully Phosphorylated GPI Anchor Pseudohexasaccharide of <i>Toxoplasma </i><i>g</i><i>ondii</i>
作者:Klaus Pekari、Denis Tailler、Ralf Weingart、Richard R. Schmidt
DOI:10.1021/jo015840q
日期:2001.11.1
stereoselectivity and good yields in the glycosylation reactions, anchimeric assistance was employed. To enable regioselective attachment of the two different phosphorus esters, the 6f-O-silyl group of 32 was first removed and the aminoethyl phosphate residue was attached. Then the MPM group was oxidatively removed, and the second phosphate residue was introduced. Unprotected 1a was then liberated in two steps:
完全磷酸化的糖基磷脂酰肌醇(GPI)锚定假六糖1a的逆合成导致了结构单元2-6,其中5和6是已知的。假二糖结构单元2的形成基于容易获得的结构单元7,该结构单元7通过衍生物11及其与已知供体12的糖基化作用,获得了所需的化合物2。结构单元3,允许所需的所有羟基进入,由甘露糖分五个步骤制备。从容易获得的前体中获得结构单元4,该结构单元4与3反应生成二糖23。决定性假六糖中间体32的合成基于23与5,然后与6,最后与2的反应。由于在糖基化反应中具有高的立体选择性和良好的收率,因此使用了嵌合助剂。为了使两种不同的磷酸酯区域选择性地连接,首先除去32的6f-O-甲硅烷基,并连接磷酸氨基乙基残基。然后,氧化除去MPM基团,并引入第二磷酸盐残基。然后分两步释放未保护的1a:用甲醇钠处理除去了乙酰基保护基团,最后,催化氢化得到了所需的目标分子,该分子可以在结构上完全分配。