Debromomarinone

The proposed biosynthesis of marinone was first reported by Murray et al. in 2018.^[3] The biosynthesis of marinone begins with 1,3,6,8-tetrahydroxynaphthalene (THN), which is known to be biosynthesized via the condensation of five malonyl-coenzyme A units followed by the aromatization of the resulting pentaketide using a type III polyketide synthase.^[4] Next, THN undergoes geranylation or farnesylation at the C-4 position, yielding 1 (Fig. 1). This transformation is catalyzed in vivo by NphB aromatic prenyltransferase in naphterpin biosynthesis^[5] or by CnqP3 or CnqP4 in marinone biosynthesis.^[6] Then, 1 undergoes oxidative dearomatization which is catalyzed by VCPO, which is a vanadium-dependent chloroperoxidase enzyme. This transformation yields compound 2. Compound 2 then undergoes two consecutive chlorinations at the C2 position, catalyzed by VCPO, to yield 4. Next, a VCPO catalyzed α-hydroxyketone rearrangement shifts the geranyl substituent from C-4 to C-3, yielding 5. Exposure of 5 to mildly basic conditions induces cyclization to yield the α-chloroepoxide, 6. This is followed by the reductive halogenation of the α-chloroepoxide to yield the hydroxynaphthoquinone, 7. Next, oxidation at the C-2 position and facile E/Z isomerization of the double bond affords the enone, 8, which undergoes a intramolecular hetero-Diels-Alder to yield debromomarinone.