Synthesis of galloyl-substituted procyanidin B4 series, and their DPPH radical scavenging activity and DNA polymerase inhibitory activity

Synthesis of galloyl-substituted procyanidin B4 series, 3-O-gallate, 3"-O-gallate and 3,3"-di-O-gallate, is described. Condensation of the electrophile derived from (+)-catechin with the nucleophile derived from (-)-epicatechin in the presence of TMSOTf as a catalyst gave procyanidin B4 3-O-gallate and 3,3"-di-O-gallate in good yields. Procyanidin B4 3"-O-gallate and procyanidin B3,3"-O-gallate were synthesized by the DCC method. Their DPPH radical scavenging activity and DNA polymerase inhibitory activity were also investigated. The results indicated that the presence of the galloyl moiety of these compounds is very important for both activities.