Total Synthesis of Proline-Rich Cyclic Octapeptide Stylissamide X

The naturally occurring proline-rich cyclic octapeptide stylissamide X is for the first time total synthesized in the present study by a two-step solid-phase/solution synthesis strategy using two different synthetic routes. In this study, all the amino acids are of L-configuration. The linear octapeptide was assembled by standard Fmoc solid-phase peptide synthesis (SPPS) and cyclization was carried out subsequently by the solution method. The target compound was purified by preparative RP-HPLC, and its structure was identified by C-13 NMR, H-1 NMR and MS.