New Protective Groups for Peptide Synthesis. 4. Chromone-Derived Protection for Amine and Carboxyl Functions

Article abstract of DOI:10.1021/jo00337a030

A new urethane-type protective group for amines, the 2-(trifluoromethyl)-6-chromonylmethylenecarbonyl (Tcroc)group (15), and a new benzyl ester type protective group for carboxylic acids, the 2-(trifluoromethyl)-6-chromonylmethylene (Tcrom) group (12), are described.The Tcroc and Tcrom groups are shown to be rapidly cleaved by neat propylamine or dilute ethanolic hydrazine and to resist cleavage by ethyl alaninate and a variety of acidic reagents.Independent removal of Tcroc or Tcrom and of Boc or tert-butyl ester groups, each in the presence of the other, is demonstrated by a synthesis of N^α-Boc methionine enkephalin.