Synthetic Studies towards Pseurotin A. Part 3. Synthesis of a related highly functionalized γ‐lactone

A new general concept for the total synthesis of pseurotin A (1), a secondary metabolite of Pseudeurotium ovalis STOLK, which possesses a highly substituted 1‐oxa‐7‐azaspiro[4.4]nonane skeleton, is presented. A key intermediate of the planned reaction sequence is the functionalized γ‐lactone 8. The corresponding protected compound 52 was prepared using (S)‐O,O‐isopropylideneglyceraldehyde (13) and the bromoacetal 14 as starting material. γ‐Lactone 52 was obtained in enantiomerically pure state in ten steps. It possesses the desired configuration.