Short-chain dehydrogenase/reductase; part of the gene cluster that mediates the biosynthesis of iso-A82775C, a enylepoxycyclohexane and biosynthetic precursor of the chloropestolide anticancer natural products (PubMed:29384350). Within the cluster, the prenyltransferase iacE prenylates siccayne to generate pestalodiol E, using dimethylallyl diphosphate (DMAPP) as cosubstrate (PubMed:29384350). The probable oxidoreductase iacF is then involved in the epoxidation of pestalodiol F to pestalodiol F, which is further converted to pestalofone A by the short-chain dehydrogenase/reductase iacG (PubMed:29384350). Iso-A82775C is subsequently generated from pestalofone A by the short-chain dehydrogenase/reductase iacC (PubMed:29384350). Iso-A82775C is further condensed with maldoxin via a Diels-Alder reaction to produce the anticancer natural products chloropestolides A to E (Probable). Secondary metabolite biosynthesis. Expression is co-regulated with the other genes from the iso-A82775C biosynthesis cluster and probably controlled by the cluster-specific transcription factors iacI and iacK. Abolishes the production of iso-A82775C, but accumulates pestalofone A. Iso-A82775C is a precursor for the biosynthesis of the anticancer natural products chloropestolides A to E via a Diesls-Alder reaction with maldoxin (PubMed:29384350). In the absence of the prenyltransferase iacE, siccayne accumulates instead of iso-A82775C and can also be condensed with maldoxin to produce chloropestolides H to K, which show also antibacterial and anticancer properties (PubMed:29384350). Belongs to the short-chain dehydrogenases/reductases (SDR) family.