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Synthesis of oligomeric epicatechin and catechin-derived procyanidins
Synthesis of oligomeric epicatechin and catechin-derived procyanidins
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机译:寡聚表儿茶素和儿茶素原花青素的合成
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摘要
Various processes are disclosed for preparing procyanidin oligomers having (4,8)-interflavan linkages. In an improved process, a tetra-O-protected-epicatechin or -catechin monomer or oligomer is coupled with a protected, C-4 alkoxy-activated-epicatechin or -catechin monomer in the presence of an acidic clay instead of a Lewis acid. In a second process, a 5,7,3′,4′-tetra-O-protected or preferably penta-O-protected-epicatechin or -catechin monomer or oligomer is reacted with a tetra-O-protected or preferably penta-O-protected-epicatechin or -catechin monomer having a thio activating group at the C-4 position; the coupling is carried out in the presence of silver tetrafluoroborate. In third process, two molecules of a penta-O-protected-epicatechin or -catechin monomer activated with a 2-(benzothiazolyl)thio group at the C-4 position are self-condensed in the presence of silver tetrafluoroborate. An improved two-step process for preparing a C-4 alkoxy activated tetra-O-benzyl-protected, 8-bromo-blocked-epicatechin or -catechin monomer is also provided. The use of naturally-derived and synthetically-prepared procyanidin (4β,8)4-pentamers to treat cancer is also disclosed.
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