ACID-CATALYZED AND ENZYME-CATALYZED CYCLIZATION REACTIONS OF (Z,E)-1(10),4-CYCLODECADIENE DERIVATIVES AS MODEL SYSTEMS FOR MELAMPOLIDES

The acid-and enzyme-catalysed cyclisations of a number of (Z,E)-1(10), 4-cyclodecadiene derivatives were investigated. In contrast to the reg ular transannular C-C bond formation as observed for (E,E)-1(10),4-cyc lodecadiene systems, these melampolide-like systems cyclised via a num ber of different reaction pathways in which the oxygen function at C-9 plays a crucial role. It was also found that these melampolide-like s ystems preferably react from the anti conformation. This finding is no t in agreement with the postulate that melampolides are intermediates in the biosynthesis of trans-fused guaianes. Molecular mechanics and d ynamics calculations indicated that the anti conformation is also the conformation in which these compounds preferably exist. (C) 1997 Elsev ier Science Ltd.