This "polymeric benzaldehyde" reversibly binds e.g. amines or diols. The resin has been used to prepare 2,5-disubstituted tetrahydrofurans via electrophilic rearrangement of isoxazolines produced by the [3+2] addition of nitrile oxides to resin bound alkenes and in the synthesis of new resins for chemical ligation and cyclization of unprotected peptides.