Acetic Acid → N-[1-Ethoxycarbonyl-3-(2-thienyl)-propyl]L-alanyl-L-proline

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Reaction Steps

4 g of type 4 A molecular sieves (powdered) are added to a mixture of L-alanyl-L-proline (0.93 g) and ethyl 2-oxo-4-(2-thienyl)-butyrate (3.18 g) in 25 ml of anhydrous ethyl alcohol. The mixture is stirred for 45 minutes at room temperature, followed by slow addition (3.5 hours) of a solution of sodium cyanoborohydride (0.785 g) in 15 ml of anhydrous ethyl alcohol and stirring overnight at room temperature. The reaction mixture is made just slightly acidic with glacial acetic acid, filtered and the filtrate conc. in vacuo to an orange oil. Extraction of a chloroform solution of this oil with 10% potassium bicarbonate, followed by re-extraction of the acidified (pH 3) bicarbonate extracts with chloroform provide, after drying and evaporation of solvent, 400 mg of the desired substituted dipeptide. The nmr spectrum (CDCl3) shows the thienyl proton as multiplet at 7.0 ppm, two active protons in broad singlet at 6.2 ppm, six methyl protons as broad multiplet 1.22-1.43 ppm range, and a series of ill-defined multiplets ranging 1.8-4.4 ppm.

Provenance & Evidence