T TOKOROYAMA; K FUJIMORI; T SHIMIZU; Y YAMAGIWA; M MONDEN; H IIO
TETRAHEDRON PERGAMON-ELSEVIER SCIENCE LTD 44 (21) 6607 - 6622 0040-4020 1988
Title full: A general method for the synthesis of clerodane diterpenoids. Stereospecific total syntheses of (±)-15, 16-epoxy-cis-cleroda-3, 13(16), 14-triene and (±)-maingayic acid 1 1 Part 22 in Synthetic Studies on Terpenic Compounds. For Part 21 see: A. Kondo, T. Ochi, H. Iio, T. Tokoroyama and M. Siro, Chemistry Lett., 1987, 1491. Ref. 2 counts as Part 18. 2 2 A preliminary report of this work has been published: T. Tokoroyama, K. Fujimori, T. Shimizu, Y. Yamagiwa and H. Iio, J. Chem. Soc., Chem. Commun., 1983, 1516. A general method for the syntheses of cis- and trans-clerodane diterpenoids has been developed and its applications to the total syntheses of both representatives 11 and maingayic acid (32) in racemic forms are described. The common Δ 4 -3-octalone intermediates 2a and 2b were prepared from 3,4-dimethyl-2-cyclohexenone by a stereospecific conjugate addition-alkylation sequence and the subsequent thermodynamically controlled annelation. The dimethylcuprate addition to 2a followed by enolate trapping afforded stereospecifically the cis-alcohol 12, from which (±)-11 has been synthesized. On the other hand hydrocyanation of 2b gave trans-intermediate 33, and then it has been converted to (±)-maingayic acid (32). © 1988.