Efficient route to optically pure polyfunctionalized cyclooctanes

A short and efficient synthesis of enantiopure highly functionalized eight-membered carbocyclic rings is described from 1,2:5,6-bis-epoxides issued from d-mannitol. The key cyclization step involves the metathesis of 1,9-diene using Grubbs’ catalyst or the pinacolic coupling of 1,8-dialdehyde resulting from the oxidative cleavage of the previous diene. In the specific case of ring-closing metathesis cyclization, the influence of a conformationally restricted diene compared to that of a flexible one has been evaluated.