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 alpha-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 H-1 NMR and HPLC analyses of the corresponding Mosher's esters. The enantiomerically pure 4-hydroxy-2-isoxazoline a-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 alpha,alpha-disubstituted polyhydroxy amino acids.