0.1 ml (0.8 mmol) of triethylamine is added to a solution containing 50 mg (0.3 mmol) of (S)-2-hydroxy-3-(1H-imidazol-4-yl)propanoic acid and 100 mg (0.3 mmol) of TBTU in 2 ml of dimethylformamide. After stirring for 1 hour at ambient temperature, 128 mg (0.3 mmol) of (R)-2-amino-1-(3-butoxy-3-o-tolyl-azetidin-1-yl)-3-(4-methoxyphenyl)propan-1-one hydro-chloride (described in Example 6.2) are added and the mixture is stirred for 72 h at ambient temperature. A 1N aqueous solution of sodium hydroxide is added and the medium is extracted with a 20/80 heptane/ethyl acetate mixture. The organic phase is dried over magnesium sulphate, filtered and concentrated. The crude product is purified by preparative thin layer chromatography (eluent: 90/10 dichloro-methane/methanol). 17 mg of (S)—N—[(R)-2-(3-butoxy-3-o-tolylazetidin-1-yl)-1-(4-methoxybenzyl)-2-oxoethyl]-2-hydroxy-3-(1H-imidazol-4-yl)propionamide are obtained in the form of a white powder with a yield of 13%.
