STEREOCHEMICAL COURSE OF THE TRANSANNULAR CYCLIZATION, IN CHLOROFORM, OF EPOXYCEMBRANOIDS DERIVED FROM THE GEOMETRICAL-ISOMERS OF (14S)-14-HYDROXY-1,3,7,11-CEMBRATETRAENES

A new cembranoid sarcophytol T (5a) was isolated from the soft coral Sarcophyton glaucum, and the structure was shown to be (14S)- 14-hydroxy-1(E), 3(Z), 7(E), 11(E)-cembratetraene, a geometrical isomer of the potent antitumor promoter sarcophytol A (1). Compound 5a and its geometrical isomers, sarcophytol N (6,1Z,3Z) and sarcophytol F (7,1E,3E), were found to be converted by autoxidation to bicyclo[9.3.0]tetradecene derivatives when kept in CHC13 solution at room temperature, in the same way as 1 (1Z,3E). The stereochemistry of each product (4 from 1 and 5a, 12 from 6, and 16 from 7) was derived by NOE analyses and by conversion of 12 and 16 to the enantiomeric ketones 17 and 18, respectively. 4-Hydroxy-1,14-epoxy 2-ene derivatives were shown to be the immediate precursors in the transannular cyclization, while cembrene C (23), the parent hydrocarbon of 1, also reacted in CHC13, giving the bicyclic derivatives 25. © 1990, American Chemical Society. All rights reserved.