Eucalyptals D and E new cytotoxic phloroglucinols from the fruits of Eucalyptus globulus and assignment of absolute configuration

摘要

Two new phloroglucinols, named eucalyptals D (>1) and E (>2), along with a related known compound (euglobal-In-3, >3) were isolated from the fruits of Eucalyptus globulus. Their structures were established on the basis of extensive spectroscopic studies, revealing that they share a common 3,5-diformyl-isopentyl phloroglucinol unit, but each is instead coupled to a different sesquiterpenoid skeleton (aromadendrene in >1, cadinene in >2, and a spirosesquiterpene in >3). Compound >1 possessed an unusual seven-membered D ring with an ether bridge between C-2 of the aromadendrene moiety and C-2′ of the aromatic unit. The absolute configuration of the isolates was defined by the comparison of experimental and calculated electronic circular dichroism (ECD) spectra. Compounds >1–3 exhibited significant in vitro cytotoxicities against a few human cancer cell lines (Huh-7, Jurkat, BGC-823, and KE-97) using the CellTiter-Glo^™ luminescent cell viability assay method.