Preparation of Sugar Amino Acids by Claisen‐Johnson Rearrangement: Synthesis and Incorporation into Enkephalin Analogues

Abstract

Abstract We have developed a convenient route for the synthesis of an unsaturated branched sugar bearing a carboxylic acid and an amino group (masked as an azide group) by employing a totally stereoselective Claisen−Johnson rearrangement as the key step. Several Met‐ and Leu‐enkephalin analogues with different substitution patterns at the N ‐ and C ‐termini were prepared by incorporating this sugar amino acid (SAA) as a substitute for the central Gly−Gly fragment of the parent pentapeptides. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)