By condensation of N-(perhydroazepin-1-ylcarbonyl)-L-leucine (V) with 4-O-benzyl-L-tyrosine tert-butyl ester (VIII) by means of HOBT and diisopropylethylamine in DMF. The two peptide intermediates (V) and (VIII) have been obtaines a follows: L-Leucine fragment (V): The carbonatation of perhydroazepine (I) with CO2 and pyridine followed by reaction with SOCl2 gives perhydroazepin-1-ylcarbonyl chloride (II), which is condensed with L-leucine benzyl ester (III) yielding the N-acylated leucine ester (IV). Finally, this compound is debenzylated by hydrogenation with H2 over Pd/C in THF to afford the target intermediate (V). Tyrosine fragment (VIII): By esterification of 4-O-benzyl-L-tyrosine (VI) with isobutylene (VII) by means of sulfuric acid in dioxane.

By condensation of N-(perhydroazepin-1-ylcarbonyl)-L-leucine (V) with 4-O-benzyl-L-tyrosine tert-butyl ester (VIII) by means of HOBT and diisopropylethylamine in DMF. The two peptide intermediates (V) and (VIII) have been obtaines a follows: L-Leucine fragment (V): The carbonatation of perhydroazepine (I) with CO2 and pyridine followed by reaction with SOCl2 gives perhydroazepin-1-ylcarbonyl chloride (II), which is condensed with L-leucine benzyl ester (III) yielding the N-acylated leucine ester (IV). Finally, this compound is debenzylated by hydrogenation with H2 over Pd/C in THF to afford the target intermediate (V). Tyrosine fragment (VIII): By esterification of 4-O-benzyl-L-tyrosine (VI) with isobutylene (VII) by means of sulfuric acid in dioxane.