Observation of heavy atom effects in the development of water soluble caged 4-hydroxy-trans-2-nonenal

During the course of our study on the photochemistry of 1-alkoxy-9,10-anthraquinones, we have developed a second generation of a caged 4-hydroxy-trans-2-nonenal (4-HNE). As we optimized the anthraquinonyl chromophore to achieve water solubility, we studied the photochemistry of various substituents to understand their effect on the photochemistry. We observed a significant heavy atom effect that severely reduced the rate of oxidative cleavage of the alkoxy group. Based on the results of our substituent study, we designed a new caged 4-HNE that is soluble under physiological conditions, and that releases 4-HNE photochemically in high yield.