Investigation of the synthetic route to pepstatin analogues by SPPS using O-protected and O-unprotected statine as building blocks.

The synthetic route to pepstatin derivatives by a solid phase peptide synthesis using either O-protected or O-unprotected statine as a building block has been investigated. Statine was prepared according to a modified literature procedure, whereas protection of its 3-hydroxyl moiety using tert-butyldimethylsilylchloride (TBSCl) provided the novel O-TBS-protected statine building block. The O-tert-butyldimethylsilyl (TBS)-protected statine approach provides an improved synthetic strategy for the preparation of statine-containing peptides as demonstrated by the synthesis of the pepstatin analogue iva-Val-Leu-Sta-Ala-Sta.