Synthesis and activity of a newly isolated analgesic pentapeptide, neo-kyotorphin.

Abstract
A newly isolated bovine brain pentapeptide, Thr-Ser-Lys-Tyr-Arg (neo-kyotorphin), which contains the Tyr-Arg (kyotorphin) unit at its carboxyl terminal portion, was synthesized by using the TFMSA-TFA-thioanisole deprotecting procedure. The synthetic peptide exhibited dosedependent analgesic activity in mice at a level approximately equal to that of Leu-enkephalin.