Hybrid PKS-NRPS synthetase; part of the gene cluster that mediates the biosynthesis of trichosetin, a trans-fused decalin-containing tetramic acid with antimicrobial activity (PubMed:28379186). The PKS module of PKS-NRPS1 together with the enoylreductase (ER) catalyze the formation of the polyketide unit which is then conjugated to L-serine by the condensation domain of the PKS-NRPS1 NRPS module (By similarity). Activity of the Dieckmann cyclase domain (RED) results in release of the Dieckmann product intermediate (By similarity). Diels-Alderase (DA) is involved in endo-selective Diels-Alder cycloaddition to form the decalin ring, leading to the production of N-desmethylequisetin also called trichosetin (By similarity). The cluster does not contain the equisetin N-methyltransferase and consequently, trichosetin is isolated as final product (PubMed:28379186). (5S)-3-[(2E,6R,8E,10E,12E)-2,6-dimethyltetradeca-2,8,10,12-tetraenoyl]-5-(hydroxymethyl)pyrrolidine-2,4-dione = trichosetin Mycotoxin biosynthesis. Expression is positively regulated by the trichosetin cluster-specific transcription activator TF22 (PubMed:28379186). Results in the production of reduced, though significant, amounts of trichosetin (PubMed:28379186). Belongs to the Diels-Alderase family.