First total synthesis of astin G

The astin family of cyclopentapeptides contains several noncoded amino acids, including β-phenylalanine, α-aminobutyric acid and several substituted prolines. The difficult cyclization of the macrocycle and the subsequent first total synthesis of a member of this family, astin G, are discussed herein. This synthesis provides a model for the syntheses of the astins which contain the highly sensitive 3,4-dichloroproline.