First total synthesis of astin G

The astin family of cyclopentapeptides contains several noncoded amino acid s, including beta-phenylalanine, alpha-aminobutyric acid and several substi tuted prolines. The difficult cyclization of the macrocycle and the subsequ ent first total synthesis of a member of this family, astin G, are discusse d herein. This synthesis provides a model for the syntheses of the astins w hich contain the highly sensitive 3,4-dichloroproline. (C) 1998 Elsevier Sc ience Ltd. All rights reserved.