3.1 g of Boc-MePhe-OH are dissolved in 30 ml of tetrahydrofuran, cooled to -20°, and 1.45 ml of N-ethylmorpholine are added with stirring followed by 1.45 ml of chloroformic acid iso-butyl ester and the mixture stirred for a further 5 minutes at -20°. A cold solution of 1.80 g of methioninol in 1 ml of tetrahydrofuran is added, the mixture left to stand for 2 hours at a temperature of from -5° to 0° and then stirred for 2 hours at room temperature. The reaction mixture is diluted with ca. 350 ml of acetic acid and washed repeatedly with water, 1 N citric acid, 10% KHCO3 and 30% NaCl solution. The organic phase is dried over Na2SO4 and evaporated, whereby Boc-MePhe-methioninol is obtained as an amorphous product.
