[reaction: see text] Lovastatin nonaketide synthase (LovB, LNKS) is an iterative type I polyketide synthase (PKS) from Aspergillus terreus that produces dihydromonacolin L (2), the biosynthetic precursor of lovastatin (1), from acetyl CoA, malonyl CoA, and S-adenosylmethionine (SAM) if the accessory protein LovC is present. In the absence of LovC, LNKS forms the conjugated pyrones 3 and 4 as truncated PKS products. Short syntheses of these pyrones provide material for the assay of LNKS activity by HPLC and radioisotope dilution analysis.