Norlichexanthone synthase; part of the gene cluster that mediates the biosynthesis of griseofulvin, an important antifungal drug that has been in use for a long time for treating dermatophyte infections (PubMed:20534346, PubMed:23978092). The first step of the pathway is the formation of the heptaketide backbone by gsfA which is initiated by priming with acetyl-CoA, followed by sequential condensations of 6 malonyl-CoA units (PubMed:20534346). O-methylation at 3-OH by gsfB leads to griseophenone D which is further methylated at 9-OH by gsfC to yield griseophenone C (PubMed:23978092). Griseophenone C is then substrate of halogenase gsfI which is responsible for the regio-specific chlorination at the C13 position to form griseophenone B (PubMed:23978092). The cytochrome P450 gsfF catalyzes the coupling of orcinol and phloroglucinol rings in griseophenone B to form desmethyl-dehydrogriseofulvin A which is further methylated at 5-OH by gsfD to yield dehydrogriseofulvin (PubMed:23978092). Finally, gsfE performs stereospecific reduction of enone 18 of dehydrogriseofulvin to afford the final product griseofulvin (PubMed:23978092). Secondary metabolite biosynthesis; terpenoid biosynthesis. Multidomain protein; including a starter unit:ACP transacylase (SAT) that selects the starter unit; a ketosynthase (KS) that catalyzes repeated decarboxylative condensation to elongate the polyketide backbone; a malonyl-CoA:ACP transacylase (MAT) that selects and transfers the extender unit malonyl-CoA; a product template (PT) domain that controls the immediate cyclization regioselectivity of the reactive polyketide backbone; and an acyl-carrier protein (ACP) that serves as the tether of the growing and completed polyketide via its phosphopantetheinyl arm (By similarity). Impairs the production of griseofulvin (PubMed:20534346, PubMed:23978092). Griseofulvin is a spirocyclic fungal natural product used in treatment of fungal dermatophytes (PubMed:13577889, PubMed:4583105).