Syntheses by the conventional method are described of Nalpha-tyrosylsecretin, [Tyr1]secretin, and Nalpha-beta-(4-hydroxyphenyl)propionylsecretin. Secretin and [Tyr6]secretin were also prepared by the synthetic route identical with those employed for construction of the above analogues. Purification of secretin and the analogues was conducted by ion-exchange column chromatography on CM-Sephadex and