Solid-phase total synthesis of trunkamide A(1).

Marine organisms are a rich source of novel, biologically active compounds. Herein, the solid-phase total synthesis of trunkamide A, currently in preclinical trials, is presented. Trunkamide A contains a thiazoline heterocycle and two residues of Ser and Thr with the hydroxy function modified as reverse prenyl (rPr). Cornerstones of the synthesis are as follows: (i) solid-phase peptide chain elongation using a quasi-orthogonal protecting scheme with tert-butyl and fluorenyl based groups, on a chlorotrityl resin; (ii) concourse of HOAt-based coupling reagents; and (iii) cyclizations in solution. Furthermore, the following synthetic steps are discussed: (i) preparation of the reverse prenyl derivatives of Ser and Thr; (ii) introduction of precursor of thiazoline as a protected amino thionoacid derivative; and (iii) formation of the thiazoline ring with DAST. All these features make this strategy particularly suitable for the large-scale synthesis of trunkamide A and other peptides containing the same motifs.