The chemistry of Eremophila spp. XIX. New cembrane diterpenes from E. granitica and E. abietina
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The isolation and structural elucidation of five new cembrane diterpenes from two Eremophila species is reported. (1R,3S,4S,7E,11Z)-3,15-Epoxy-19-oxocembra-7,11-dien-18-oic acid (3) and (1R,3S,4S,7Z,11Z)-3,15-epoxycembra-7,11-dien-18-oic acid (7) were isolated from E. granitica, and dimethyl(1R,3S,4S,7E,11Z)-3,15-epoxycembra-7,11-diene-18,19-dioate (16), (1R,3S,4S,8R,11Z)-3,15-epoxycembr-11-ene-18,19-dioic acid (14) and its dimethyl ester were isolated from E. abietina. Structural studies on the diol derived from (14) were carried out by single-crystal X-ray diffraction analysis.