Synthesis of Enkephalin Analog with Leucinthiol at C-Terminus as Probe for Thiol Group in Opiate Receptors

Abstract

Abstract Enkephalin analog with thiol group at C-terminus, [D-Ala2, Leu(CH2SH)5]enkephalin, was synthesized as possible probe for the essential thiol group in opiate receptors. In order to protect the free SH group of leucinthiol, oxidized Boc-l-leucinthiol dimer was prepared from l-leucinol (2-amino-4-methyl-1-pentanol) to elongate the enkephalin sequence. SH-Containing monomeric enkephalin analog was obtained from dimer by treatment with zinc in 50% AcOH, and it exhibited a high affinity for mu opiate receptors.