Isobutyl chloroformate → N[(1,1-dimethylethoxy)carbonyl]-2,6-dimethyltyrosyl-N-(3-phenyl propyl)-Nalpha-(2-propenyl)-D-alaninamide

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Reaction Steps

N-Allyl-(D)-alanylphenylpropylamide (5.00 g, 20.3 mmol) replaced (D) alanyl-phenylpropylamide in the mixed anhydride synthesis described in Example 2. It was reacted using Boc-2,6-dimethyl-tyrosine (6.28 g, 20.3 mmol) N-methyl morpholine (2.05 g, 20.3 mmol) and isobutylchloroformate (2.77 g, 20.3 mmol). Dimethylformamide replaced CH2Cl2 as the solvent. The reaction mixture was worked up as in Example 2 and the resultant oil (10.62 g) was purified by column chromatography on Woelm silica eluting with 3 to 5% methanol-methylene chloride and the diasteromers were separated:

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