A convenient route for the synthesis of oxacyclobutapentalene, the tricyclic bridged core structure present in bioactive marine diterpene bielschowskysin and the polyketide hippolachnin A, is reported. The key steps involve ring closing metathesis of a triene derived from D-mannitol to produce selectively the dihydrofuran derivative instead of the cyclopentene derivative and a Cu(I)-catalyzed intramolecular [2+2]photocycloaddition of the dihydrofuran derivative.

Ring closing metathesis of acyclic trienes that can provide oxacycles or carbocycles has been investigated. It was found that a substituent on one of the alkene units determines the reaction course to provide either oxacycles or carbocyles exclusively irrespective of the ring size of the resulting compounds.

Development of a route for the synthesis of the core structure of galiellalactone is described. The key step involves a ring-closing enyne metathesis of an allyl propargyl ether to produce a dihydro furano diene with a latent dienophile. The dienophile, when generated from this latent functionality, underwent an in situ intramolecular Diels–Alder reaction to produce the tricyclic skeleton present in galiellalactone