Reactive intermediates in peptide synthesis. ortho-Nitrophenyl N-alpha-para-toluenesulfonyl-alpha-aminoisobutyrate

The preparation, characterization, and molecular and crystal structures of the title compound [IUPAC name: 2-nitrophenyl 2-methyl-2-(para-toluenesulfonylamino)propanoate], C17H18N2O6S, are reported. The phenyl group is almost perpendicular to the plane of the adjacent ester moiety. One O atom of the nitro group is wedged between the two ester O atoms. The implications of this peculiar conformation for the chemistry of ortho-nitrophenyl esters in peptide synthesis are discussed.