The regioselective synthesis of chafurosides A (1) and B (2) from the same methyl ketone 5 was accomplished using a novel protecting group strategy. Both flavone rings were constructed from β-diketone intermediate 4, which was readily obtained by condensation of an acyl donor and ketone 5. Construction of the dihydrofuran ring was achieved via an intramolecular Mitsunobu reaction.

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A practical synthesis of nobiletin, a polymethoxylated citrus flavone, was accomplished by utilizing our novel flavone synthesis. Synthetic nobiletin was labelled by selective demethylation and rapid incorporation of (11)C atom. Positron emission tomography images successfully visualized the brain distribution, which may provide therapeutic benefits in the treatment of Alzheimer's disease.

We present a practical synthesis of the polymethoxylated citrus flavone nobiletin that is suitable for use on a hundred gram scale. Ready availability of this compound and its derivatives will aid detailed chemical-biological investigations of their biological activities, including activation of signaling via the cAMP-dependent protein kinase A/extracellular signal-related protein kinase/cAMP response element-binding protein pathway.

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