Viminalins A-O: Diverse [3+2] hybrids of acylphloroglucinol and α-phellandrene from the fruits of Callistemon viminalis

Abstract Viminalins A-O ( 1 – 15 ), a series of new [3+2] hybrids of acylphloroglucinols and α -phellandrene featured a 2,3-dihydrobenzofuran core were isolated from the fruits of Callistemon viminalis . Their structures were established on the basis of extensive analysis of NMR spectra, circular dichroism, and X-ray crystallography. An oxidative [3+2] cycloaddition between acylphloroglucinol and monoterpene was speculated as the key step in the biosynthetic pathway. Bioactivities screen indicated that compound 6 exhibited moderate cytotoxic activity.