NAD(P)H:quinone reductase 1 (QR1) belongs to a class of enzymes called cytoprotective enzymes. It exhibits its cancer protective activity mainly by inhibiting the formation of intracellular semiquinone radicals, and by generating α-tocopherolhydroquinone, which acts as a free radical scavenger. It is therefore believed that QR1 inducers can act as cancer chemopreventive agents. Resveratrol (1) is a naturally occurring stilbene derivative that requires a concentration of 21 μM to double QR1 activity (CD = 21 μM). The stilbene double bond of resveratrol was replaced with a thiadiazole ring and the phenols were eliminated to provide a more potent and selective derivative 2 (CD = 2.1 μM). Optimizing the substitution pattern of the two phenyl rings and the central heterocyclic linker led to a highly potent and selective QR1 inducer 9o with a CD value of 0.087 μM.
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