Biosynthesis of Tropolones in Penicillium stipitatum. VIII.¹ The Utilization of Polyketide Lactones for Tropolone Formation

Cross‐reaction of chalcone synthase and stilbene synthase overexpressed in Escherichia coli

“…Even though aldol condensation of triketo acids can proceed in weakly acidic (pH 5) aqueous buffer, the products are fairly stable β‐resorcylic acids [18]. Decarboxylation of aromatic carboxylic acids such as conversion of 6‐styryl‐β‐resorcylic acid to pinosylvin and of orsellinic acid to orcinol have been achieved either by heat (180°C) [18,19], by alcoholic KOH [20] or by a decarboxylase [21]. It should be noted that stilbene carboxylic acids, though found in nature [22], have not been detected from the STS reaction mixture.…”

Catalytic role of the C-terminal domains of a fungal non-reducing polyketide synthase

“…Bentley and Zwitkowits studied the biosynthesis of the tropolones stipitatic and stipitatonic acid in P. stipitatum during the late 1960s. 8 They knew that methionine was a precursor of these compounds, but not that methylorcinaldehyde was an intermediate-this was not elucidated until 1974. 4 They fed the MeT inhibitor ethionine to growing cultures of P. stipitatum and observed that production of the tropolones was inhibited while tri-(T3AL, 5) and tetraacetic acid lactones (T4AL, 6) were produced, presumably by a PKS with an inhibited CMeT domain.…”

“…4 They fed the MeT inhibitor ethionine to growing cultures of P. stipitatum and observed that production of the tropolones was inhibited while tri-(T3AL, 5) and tetraacetic acid lactones (T4AL, 6) were produced, presumably by a PKS with an inhibited CMeT domain. 8 We thus studied the extracts of A. oryzae expressing pASPKS1-DMR for the production of these compounds. T3AL 5 is commercially available and in tests we could detect it at concentrations as low as 10 mg L À1 in fermentation cultures.…”

α‐Pyrones and Pyranes from the Plant Pathogenic Fungus Pestalotiopsis scirpina

“…Scirpyrone B (2), however, differs from the known α-pyrones in possessing a butyl group attached to C-7, and is presumably the ring-opened product of 1. [33] The biosynthesis of 1-7 might proceed similarly to those of the known examples, with that of 1-3 illustrated in Scheme 1. Biosynthetic studies of some α-pyrones demonstrated that they originated from Claisen condensations of acetyl CoA and malonyl CoA/propionyl CoA.…”