Enantiomerenreine 3,7‐Dioxa‐2‐azabicylo[3.3.0]octane durch intramolekulare 1,3‐dipolare Cycloaddition von Nitronen

Enantiomerically Pure 3,7‐Dioxa‐2‐azabicyclo[3.3.0]octanes by Intramolecular 1,3‐Dipolar Cycloaddition of Nitrones Starting with chiral non‐racemic esters of lactic acid 7 and mandelic acid 8 , respectively, chiral nitrones 4 have been prepared. They spontaneously undergo an intramolecular cycloaddition which proceeds with asymmetric induction by the chiral center yielding exclusively the bicyclic compounds 5 in enantimerically pure form. Reductive opening of the isoxazolidine ring affords tetrahydrofuran derivatives 13 with an γ‐amino alcohol group. Reaction of 13 with (‐)‐camphanoyl chloride gives the esters 14. Their 1 H‐NMR spectra reveal a diastereomeric purity of at least 98%.