Abstract
The stereoselective 1,3-dipolar cycloaddition between (Z)-1,4-dichloro-2-butene and a menthone-derived nitrone led to the corresponding isoxazolidine. Regioselective azidation of a single chlorine atom followed by another Cu(I)-catalyzed azide–alkyne 1,3-dipolar cycloaddition (CuAAC) induced enantiopure 1,2,3-triazolyl-functionalized isoxazolidines. The subsequent acidic cleavage of the menthone chiral auxiliary and reductive cleavage of the isoxazolidine N–O bond triggered an intramolecular cyclization through the displacement of the second chlorine. This rapid and stereoselective synthetic strategy provided reliable access to a series of enantiopure 3-substituted 4-hydroxyproline derivatives.
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