23.3 ml (18.9 g=157 mMol) pivaloyl chloride and 48 ml (28.9 g=286 mMol) triethylamine are added to a solution of 35 g (143 mMol) BOC-MeLeu-OH in 500 ml chloroform and the mixture stirred for 2 hrs. at room temperature under a nitrogen atmosphere. 30.7 g (171 mMol) H-Ala-Bzl dissolved in 300 ml chloroform are then added and the reaction mixture stirred for a further 2 hrs. at room temperature, again under a nitrogen atmosphere. The product is purified in accordance with the technique of example 1a) to yield the title compound: rotation, [α]D25 =-59.4° (c=1.0 in chloroform).
