A novel 7(6→2)abeoabietane-type diterpene, obtusanal, from the Heartwood of Chamaecyparis obtusa var. formosana

A novel 7(6→2)abeoabietane-type diterpene, obtusanal (1), together with a known 12-hydroxy-6,7-secoabieta-8,11,13-triene-6,7-dial (2) isolated from the heartwood of Chamaecyparis obtusa var. formosana, were elucidated on the basis of 2D-NMR data. The biosynthesis of 1 was proposed deriving from 12-hydroxy-3-oxo-6,7-secoabieta-8,11,13-triene-6,7-dial (6) via aldol condensation.