Metabolic products of Phomopsis oblonga. Part 2. Phomopsolide A and B, tiglic esters of two 6-substituted 5,6-dihydro-5-hydroxypyran-2-ones

Phomopsolide A and B, two boring/feeding deterrents for elm bark beetles, produced in vitro by the fungus Phomopsis oblonga, are shown to be (5S,6S)-5,6-dihydro-6-(4-hydroxy-3-oxopent-1Z-enyl)-5-(2-methylbut-2E-enoyloxy)-2H-pyran-2-one and (5S,6S)-5,6-dihydro-6-[(3S,4S)-3,5-dihydroxypent-1E-enyl)-5-(2-methylbut-2E-enoyloxy)-2H-pyran-2-one, respectively. Another active compound, (–)-6-(4-hydroxy-3-oxopent-1E-enyl)-2H-pyran-2-one, was also isolated but is considered to be an artefact.