d-Mannitol as the Chiral Source for the EPC Synthesis of Both Enantiomers of 3-Ethoxycarbonyl-4-hydroxy-2-isoxazolines and Highly Functionalized Tricyclic Systems

The EPC preparation of both enantiomers of cis- and trans 5-substituted 4-hydroxy-2-isoxazoline 2-oxides has been achieved in an enantiodivergent fashion starting from d-mannitol through the application of the tandem nitroaldol-cyclization reaction to enantiomerically pure α-mesyloxyaldehydes. These stereochemically labile aldehydes have been generated in situ and reacted under very mild domino conditions. Enantiomeric purity of the products has been assessed by 1H NMR and HPLC analyses of the corresponding Mosher's esters. The enantiomerically pure 4-hydroxy-2-isoxazoline 2-oxides have been employed as pivotal intermediates for the EPC preparation of the corresponding deoxygenated derivatives and highly functionalized tricyclic systems (HFTS) 1, useful for the preparation of 2-aminopolyols and α,α-disubstituted polyhydroxy amino acids.