Novel ent-Abietane Diterpenoids from Isodon eriocalyx var. laxiflora

Abstract Two novel ent ‐abietane diterpenoids, 3 α ,20‐epoxy‐6 β ‐hydroxy‐1,7‐dioxo‐ ent ‐abiet‐15(17)‐en‐16‐oic acid ( 1 ) and ent ‐abieta‐7,15(17)‐diene‐3 β ,16,18‐triol ( 2 ) were isolated from Isodon eriocalyx var. laxiflora. Their structures were determined by extensive spectroscopic analysis and confirmed by X‐ray crystallography. Compound 1 is an unprecedented example that establishes that a naturally occurring ent ‐abietane diterpenoid can have an oxygenation pattern almost identical to those of 3 α ,20‐epoxy‐ ent ‐kaurane diterpenoids.