Synthesis and spectral studies of natural chlorins having antioxidative activity

Abstract

Starting from pheophorbide a methyl ester (1), a degradation product of chlorophyll a, novel natural antioxidants of chlorophyll a related chlorins 3, 5(S), 5(R), 8(R), 9-13 have been synthesized in high yields. Key steps involve formation of 5(R) and 5(S) via a DBU-promoted asymmetric hydroxylation of 3, and regioselective periodate oxidations of 5 to 8(R) and 9.