The new antifungal strobilurins I (1) and K (19) are 3,4-dihydro-2H- benzo[b][1,4]dioxepin derivatives. Their structure and stereochemistry was determined by degradation to aldehyde 3. Both enantiomers of 3 were synthesised and the absolute configurations assigned by the high-field1H NMR variant of Mosher's method. (S)-3 is identical with the compound derived from the natural products. In the course of those investigations the epoxide structures 15, 16 and 17 previously assigned to strobilurin D, hydroxystrobilurin D and 9-methoxystrobilurin K have to be changed in 18, 21 and 20, respectively. All these compounds possess the same benzodioxepin core structure and (S)-configuration as strobilurin I (1).
Hellwig, V., Dasenbrock, J., Klostermeyer, D., Kroiß, S., Sindlinger, T., Spiteller, P., … Anke, T. (1999). New benzodioxepin type strobilurins from basidiomycetes. Structural revision and determination of the absolute configuration of strobilurin D and related β-methoxyacrylate antibiotics. Tetrahedron, 55(33), 10101–10118. https://doi.org/10.1016/S0040-4020(99)00563-3