Hormone‐Receptor Interactions. Synthesis of a biologically active cysteinyl‐angiotensin derivative and its use for the preparation of spin‐labelled and polymer‐supported molecules

Abstract (N‐t‐Butoxycarbonyl‐S‐acetamido‐methyl‐ L ‐cysteinyl)‐[1‐ asparagine, 5‐valine]‐angiotensin II ( 2 ) was prepared from [1‐asparagine, 5‐valine]‥angiotensin II ( 1 ). With respect to enhancement of rat blood pressure, it is a full agonist displaying about 20–25% of the potency of 1 . The sulfur atom of the cysteine group represents a specific nucleophile by which the hormone can easily be attached to other molecules in a well‐defined manner. Thus, 2 has been added to N‐substituted maleimides through its (deprotected) thiol group to produce the spin‐labelled derivative 3 :{N‐ t ‐butoxy‐carbonyl‐S‐[N‐(1‐oxy‐2,2,5,5‐tetramethyl‐ pyrrolidin‐3‐yl‐methyl)‐imidosuccin‐3‐yl]‐ L ‐cysteinyl}‐[1‐asparagine,5‐valine]‐angiotensin II, and the polymer‐supported derivative 6 : S‐(N‐{5‐[7‐(sepharosyl‐oxy‐carbonimidoyl‐amino)‐4‐azaheptylcarbamoyl]‐pentyl}‐imidosuccin‐3‐yl)‐ L ‐cysteinyl‐[1‐asparagine, 5‐valine]‐angiotensin II. The ESR. spectra of 3 in different solvents, and its principal NMR. characteristics, are reported. We are using the compound for studying its interaction with receptor molecules and for purification of target cells and membrane vesicles by affinity aggregation.