Mario WibowoVilailak PrachyawarakornThammarat AreeSuthep WiyakruttaChulabhorn MahidolSomsak RuchirawatPrasat KittakoopChulabhorn Graduate InstituteChulabhorn Research InstituteChulalongkorn UniversityMahidol UniversitySouth Carolina Commission on Higher Education2018-11-092018-11-092014-01-01European Journal of Organic Chemistry. Vol.2014, No.19 (2014), 3976-3980109906901434193X2-s2.0-84903287004https://repository.li.mahidol.ac.th/handle/20.500.14594/33668The new tricyclic and spirobicyclic norsesquiterpenes 1 and 2 and the new nor-chamigrane endoperoxide 3, together with the known sesquiterpenes steperoxide A (4), merulin B (5), and merulin C (6), were isolated from the endophytic fungus Pseudolagarobasidium acaciicola. The structures and absolute configurations of 1-3 were determined by analysis of spectroscopic data, as well as by single-crystal X-ray analysis. Compound 1 has a previously unobserved 6/5/5 fused tricyclic ring system, in which the five-membered (middle) ring is, as revealed by X-ray analysis, perpendicular to a six-membered ring. Compound 2 possesses a hitherto unknown 5/6 fused spirobicyclic ring system. The cytotoxic activities of the isolated compounds 1-6 were evaluated. Tricyclic and spirobicyclic norsesquiterpenes 1 and 2 were isolated from the endophytic fungus Pseudolagarobasidium acaciicola. The absolute configurations of 1 and 2 were addressed by single-crystal X-ray analysis. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Mahidol UniversityChemistryArticleSCOPUS10.1002/ejoc.201402262