Two synthetic routes towards 3,6-dimethyl-8-oxo-9-oxa-bicyclo[4,3,0]non-2-ene , a crucial intermediate in the synthesis of the sesquiterpenoid mould metabolite trichodermin, are discussed. The strategy and ultimate approach towards the most widely distributed sesquiterpenoid component of the tricho-thecanes, verrucarol, via 3-methyl-6-hydroxymethyl-8-oxo-9-oxabicyclo[4,3,0]non-2-ene,are fully described.