Procyanidin oligomers. A new method for 4→8 interflavan bond formation using C8-boronic acids and iterative oligomer synthesis through a boron-protection strategy
作者:Eric G. Dennis、David W. Jeffery、Martin R. Johnston、Michael V. Perkins、Paul A. Smith
DOI:10.1016/j.tet.2011.10.039
日期:2012.1
Interest in the synthesis of procyanidin (catechin or epicatechin) oligomers that contain the 4→8 interflavan linkage remains high, principally due to research into their health effects. A novel coupling utilising a C8-boronic acid as a directing group was developed in the synthesis of natural procyanidin B3 (i.e., 3,4-trans-(+)-catechin-4α→8-(+)-catechin dimer). The key interflavan bond was forged using
含有4→8黄酮键的原花青素(儿茶素或表儿茶素)低聚物的合成兴趣仍然很高,这主要是由于对其健康影响的研究。在天然原花青素B3(即3,4-反式-(+)-儿茶素-4α→8-(+)-儿茶素二聚体)的合成中,开发了利用C8-硼酸作为指导基团的新型偶联。使用新颖的路易斯酸促进的C4醚6与C8硼酸16的偶合来锻造键间键,以提供具有高非对映选择性的α-连接的二聚体。通过使用硼保护基,新的偶联步骤扩展到了类似于天然原花青素C2的被保护的原花青素三聚体的合成。