Cadinane and carotane derivatives from the marine algicolous fungus Trichoderma virens RR-dl-6-8

Eight cadinane derivatives, trichocadinins H − N (1–7) and methylhydroheptelidate (8), and two carotane derivatives, 14-O-methyltrichocarotin G (9) and 14-O-methyl CAF-603 (10), including eight new ones (1–6, 9, and 10), were isolated from the culture of Trichoderma virens RR-dl-6-8 obtained from the organohalogen-enriched marine red alga Rhodomela confervoides. Their structures and relative configurations were established by analysis of NMR and mass spectroscopic data, and the absolute configurations were assigned on the basis of ECD curves, highlighted by the ECD diversity of carboxylic acid derivatives. Among the isolates, 1 with a halogen atom and 8, a new naturally occurring compound, are 2,3-seco-cadinane sesquiterpenes, and the epimeric 2 and 3 feature a 2-nor-cadinane skeleton. A commercially-sourced compound with the same planar structure as that of 7 has been reported in a patent, but its configuration was not given. Compounds 1–10 exhibited growth inhibition of some marine phytoplankton species. [Display omitted] •Eight undescribed compounds (1–6, 9, and 10), one new naturally-occurring compound (8), and trichocadinin N (7) were obtained from Trichoderma virens RR-dl-6-8.•This fungus is the second organohalogen-producing T. virens strain, and 1–10 with 2,3-seco-cadinane, 2-nor-cadinane, cadinane, and carotane frameworks add the molecular diversity of secondary metabolites from this fungal species.•These metabolites afford valuable model molecules for the ECD analysis of carboxylic acid derivatives.