AT2-Selective Angiotensin II Analogues Containing Tyrosine-Functionalized 5,5-Bicyclic Thiazabicycloalkane Dipeptide Mimetics

This paper reports the synthesis of two angiotensin II analogues with tyrosine-functionalized 5,5-bicyclic thiazabicycloalkane dipeptide mimetics replacing the Tyr4-Ile5 residues. The preparation of these analogues relies on the synthesis and incorporation of an α,α-disubstituted chimeric amino acid derivative and on-resin bicyclization to a cysteine residue. The synthesized analogues both displayed high angiotensin AT2/AT1 receptor binding preferences and had AT2 receptor affinities in the same low nanomolar range as angiotensin II itself. Conformational analysis, using experimental constraints derived from NMR studies, indicated that the Tyr4 and His6 residues in one of the angiotensin II analogues were in close proximity to each other.