Diels–Alder route to potential trichothecene precursors

2-Methylbut-3-yn-2-ol (9) is efficiently converted into 6-formyl-3,6-dimethylcyclohex-2-enyl acetate (4b) and into 6-acetyl-3,6-dimethylcyclohex-2-enyl acetate (4c)via highly regio- and stereo-selective Diels–Alder cycloadditions of 3-methylbuta-1,3-dienyl acetate (2b). The cycloadduct (4b) is converted by base into 4a,5,6,8a-tetrahydro-4a,7-dimethylcoumarin (13b), whilst the cycloadduct (4c) yields 2,3,4a,5,6,8a-hexahydro-2-hydroxy-2,4a,7-trimethylchroman-4-one (15), the structure of which was confirmed by X-ray analysis. Both (13b) and (15) possess a number of structural features of the trichothecenes and may be of value in their total synthesis.