Synthesis of the cyclic heptapeptide axinellin A

The first synthesis of the naturally occurring cyclic peptide axinellin A has been achieved. Cyclization and subsequent deprotection of linear precursors containing either a t-butyl protected Thr residue or a Thr(Ψ^Me,Mepro) derivative gave a cyclic peptide, identical in all respects to the naturally occurring material, with the exception that the synthetic peptide does not exhibit the cytotoxic activity reported for the natural product.