Diterpenoids of Roylea calycina(Roxb.) Briq.

The structures of three new diterpenes, calyone, calyenone, and precalyone, isolated from the aerial portion of Roylea calycina have been shown to be 3-acetoxy-15,16-epoxy-9-hydroxylabda-1 3(16),14-dien-7-one (2), 3-acetoxy-15,16-epoxylabda-8,13(16),14-trien-7-one (5), and 3-acetoxy-9,13;15,16-diepoxylabda-14-en-7-one (7), respectively, by chemical and spectroscopic studies. Precalyone showed antitumor activity against P-388 lymphocytic leukaemia.