A 5-MEMBERED ENANTIOPURE CYCLIC NITRONE FROM MALIC-ACID BY REGIOSELECTIVE OXIDATION OF CYCLIC HYDROXYLAMINE - SYNTHESIS OF (1S,7S,8AR)-OCTAHYDRO-1,7-DIHYDROXYINDOLIZINE

The chiral optically pure five-membered 3-tert-butoxy-1-pyrroline N-ox ide (1) was synthesized by a convenient five-step procedure from dieth yl L-malate. The key step is the regioselective HgO dehydrogenation of the N-hydroxypyrrolidine 6 obtained by double-nucleophilic displaceme nt of a (bis)mesylate with hydroxylamine. A rationalization of the obs erved regioselectivity of the oxidation by studying the oxidation of a deuterated N-hydroxypyrrolidine 20 is reported. Nitrone 1 has been ap plied to the synthesis of a new (1S,7S,8aR)-1,7-dihydroxyindolizidine (28) via 1,3-dipolar cycloaddition strategies.