benzyl 2-oxo-4-phenylbutanoate

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of L-alanyl-L-proline (167 mg) and benzyl 2-oxo-4-phenylbutyrate (1.20 g) in 5 ml of ethanol is stirred at room temperature with 3 g of powdered molecular sieves, type 4A. Sodium cyanoborohydride (75 mg) is then added in portions over the course of three hours. The product is purified by absorption on strong cation exchange resin and elution with 2% pyridine in water. After passage through a gel filtration (LH-20) column 220 mg of N-(1-benzyloxycarbonyl-3-phenylpropyl)-L-alanyl-L-proline is obtained as a mixture of isomers. Thin layer chromatography on silica gel eluted with 1 EtOAc, 1 n-butanol, 1 H2O, 1 HOAc shows one main spot, Rf 0.71. Isomers are separated using reverse phase HPLC to yield N-(1(S)-benzoyloxycarbonyl-3-phenylpropyl)-L-alanyl-L-proline. The product is purified by absorption on strong cation exchange resin and elution with 2% pyridine in water After passage through a gel filtration (LH-20) column 220 mg of N-(1-benzyloxycarbonyl-3-phenylpropyl)-L-alanyl-L-proline is obtained as a mixture of isomers Thin layer chromatography on silica gel eluted with 1 EtOAc, 1 n-butanol, 1 H2O, 1 HOAc Isomers are separated

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of L-alanyl-L-proline (167 mg) and benzyl 2-oxo-4-phenylbutyrate (1.20 g) in 5 ml of ethanol is stirred at room temperature with 3 g of powdered molecular sieves, type 4A. Sodium cyanoborohydride (75 mg) is then added in portions over the course of three hours. The product is purified by absorption on strong cation exchange resin and elution with 2% pyridine in water. After passage through a gel filtration (LH-20) column 220 mg of N-(1-benzyloxycarbonyl-3-phenylpropyl)-L-alanyl-L-proline is obtained as a mixture of isomers. Thin layer chromatography on silica gel eluted with 1 EtOAc, 1 n-butanol, 1 H2O, 1 HOAc shows one main post, Rf 0.71. Isomers are separated using reverse phase HPLC to yield N-(1(S)-benzyloxycarbonyl-3-phenylpropyl)-L-alanyl-L-proline. The product is purified by absorption on strong cation exchange resin and elution with 2% pyridine in water After passage through a gel filtration (LH-20) column 220 mg of N-(1-benzyloxycarbonyl-3-phenylpropyl)-L-alanyl-L-proline is obtained as a mixture of isomers Thin layer chromatography on silica gel eluted with 1 EtOAc, 1 n-butanol, 1 H2O, 1 HOAc Isomers are separated

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of 200 mg. of 1-(L-alanyl)-4-(S)-(phenylthio)-L-proline and 1.1 grams of benzyl 2-oxo-4-phenylbutyrate in 8 ml. of ethanol is stored at room temperature with 3 grams of powdered molecular sieves (type 4A). Over the course of three hours, 75 mg. of sodium cyanoborohydride is added. The reaction mixture is filtered and concentrated under reduced pressure. The residue is purified by absorption on a strong cation exchange resin and elution with 2% pyridine in water. After passage through a gel filtration column, the desired product, 1-[N-(1-benzyloxycarbonyl-3-phenylpropyl)-L-alanyl]-4-(S)-(phenylthio)-L-proline, is obtained as a mixture of isomers that can be separated by high performance liquid chromatography. Over the course of three hours, 75 mg The reaction mixture is filtered concentrated under reduced pressure The residue is purified by absorption on a strong cation exchange resin and elution with 2% pyridine in water After passage through a gel filtration column