The photocycloaddition of olefins with carbonyls is
of fundamental interest and practical importance in C=C bond location in
unsaturated lipids. However, the traditional UV light activated [2+2]
photocycloaddition reaction suffers side reactions and potential health damage.
Here, we reported the first example of visible-light activated [2+2] photocycloaddition of anthraquinone with unsaturated
lipids. This reaction showed great capability for locating the C=C bonds in
various kinds of monounsaturated and polyunsaturated lipids by combining with
tandem mass spectrometry (MS), such as fatty acids, phospholipids and
glycerides. Based on this developed reaction, a workflow with liquid
chromatography tandem MS method was developed for the global identification of
unsaturated lipids in human serum, and 86 of monounsaturated and complicated
polyunsaturated lipids were identified with definitive positions of C=C bonds.
This approach provides new insights both on the photocycloaddition reactions
and the structural lipidomics.
