2-(butanoylamino)propanoic acid

Conditions: temp:50.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: The compound of formula VI (3.18 g, 0.02 mol) was dissolved into dried tetrahydrofuran (20 mL), and DMAP (0.08 g, 0.6 mmol) and pyridine (5 mL) were added therein. The mixture was heated for 30 minutes at 50° C., cooled, and slowly dropped therein with ethyl oxalyl monochloride (5.46 g, 0.04 mol) under ice bath. After the dropping, the mixture was heated for 4 hours at 70° C., filtered to remove the solid, and evaporated under reduced pressure to remove the solvent. Water (40 mL) was added therein, and the solution was extracted with ethyl acetate (75 mL×3). The liquid was separated, the combined organic phase was washed with water (30 mL) and saturated saline (30 mL×2) respectively, dried over anhydrous sodium sulfate, and rotarily evaporated to remove the solvent therein. NaHCO3 (1.26 g, 0.015 mol) and methanol (20 mL) were added therein, and the mixture was refluxed for 2 hours, filtered, and evaporated under reduced pressure to remove solvent to obtain a yellow oil, i.e., ethyl 3-butyramido-2-oxo-butyrate, which was directly used in the next step without separation. were added cooled slowly dropped After the dropping, the mixture was heated for 4 hours at 70° C. filtered to remove the solid evaporated under reduced pressure to remove the solvent Water (40 mL) was added the solution was extracted with ethyl acetate (75 mL×3) The liquid was separated the combined organic phase was washed with water (30 mL) and saturated saline (30 mL×2) respectively dried over anhydrous sodium sulfate rotarily evaporated to remove the solvent the mixture was refluxed for 2 hours filtered evaporated under reduced pressure to remove solvent

Conditions: temp:50.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: The compound of formula VI (9.54 g, 0.06 mol) was dissolved into dried tetrahydrofuran (60 mL), and DMAP (0.24 g, 2.0 mmol) and pyridine (15 mL) were added therein. The mixture was heated for 30 minutes at 50° C., cooled, and slowly dropped with ethyl oxalyl monochloride (16.4 g, 0.12 mol) under an ice bath. After the dropping, the mixture was heated for 4 hours at 70° C., filtered to remove the solid, and evaporated to remove the solvent under reduced pressure. Water (100 mL) was added therein, and the product was extracted with ethyl acetate (120 mL×3). The liquid was separated, and the combined organic phase was washed by water (90 mL) and saturated saline (50 mL×2) respectively, dried over anhydrous sodium sulfate, and rotarily evaporated to remove the solvent. NaHCO3 (3.8 g, 0.045 mol) and methanol (50 mL) were added therein, and the reaction mixture was refluxed for 2 hours, filtered, and evaporated off the solvent under reduced pressure to obtain a yellow oil, i.e., ethyl 3-butyramido-2-oxo-butyrate, which was directly used in the next step without separation. were added cooled After the dropping, the mixture was heated for 4 hours at 70° C. filtered to remove the solid evaporated to remove the solvent under reduced pressure Water (100 mL) was added the product was extracted with ethyl acetate (120 mL×3) The liquid was separated the combined organic phase was washed by water (90 mL) and saturated saline (50 mL×2) respectively dried over anhydrous sodium sulfate rotarily evaporated to remove the solvent the reaction mixture was refluxed for 2 hours filtered evaporated off the solvent under reduced pressure

Conditions: temp:50.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: The compound of formula VI (3.18 g, 0.02 mol) was dissolved into dried tetrahydrofuran (20 mL), followed by addition of DMAP (0.08 g, 0.6 mmol) and pyridine (5 mL) therein. The mixture was heated for 30 minutes at 50° C., and then cooled. Under ice bath, ethyl oxalyl monochloride (5.46 g, 0.04 mol) was slowly dropped therein. After the dropping, the mixture was heated for 4 hours at 70° C. The solid was filtered off and the solvent was evaporated off under reduced pressure. Water (40 mL) was added therein, and the product was extracted by using ethyl acetate (75 mL×3). The liquid was separated, and the combined organic phase was washed by water (30 mL) and saturated saline (30 mL×2) respectively, and dried over anhydrous sodium sulfate. After the solvent therein was removed by rotary evaporation, NaHCO3 (1.26 g, 0.015 mol) and methanol (20 mL) were added therein, and the mixture was refluxed for 2 hours. After filtration, the solvent was removed by evaporation under reduced pressure to give a yellow oil, i.e., ethyl 3-butyramido-2-oxo-butyrate, which is directly used in the next step without purification. cooled After the dropping, the mixture was heated for 4 hours at 70° C The solid was filtered off the solvent was evaporated off under reduced pressure Water (40 mL) was added the product was extracted The liquid was separated the combined organic phase was washed by water (30 mL) and saturated saline (30 mL×2) respectively dried over anhydrous sodium sulfate were added the mixture was refluxed for 2 hours After filtration the solvent was removed by evaporation under reduced pressure

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 22.27 g (250 mmol) of D,L-alanine and 55.66 g (550 mmol) of triethylamine are dissolved in 250 ml of dichloromethane, and the solution is cooled to 0° C. 59.75 g (550 mmol) of trimethylsilyl chloride are added dropwise, and the solution is stirred at room temperature for 1 hour and at 40° C. for one hour. After cooling to −10° C., 26.64 g (250 mmol) of butyryl chloride are added dropwise, and the resulting mixture is stirred at −10° C. for 2 hours and at room temperature for one hour. With ice-cooling, 125 ml of water are added dropwise, and the reaction mixture is stirred at room temperature for 15 minutes. The aqueous phase is evaporated to dryness, the residue is triturated with acetone and the mother liquor is filtered off with suction. Following removal of the solvent, the residue is chromatographed. The resulting product is dissolved in 3N aqueous sodium hydroxide solution, and the resulting solution is evaporated to dryness. The residue is taken up in conc. HCl and again evaporated to dryness. The residue is triturated with acetone, the precipitated solid is filtered off with suction and the solvent is removed under reduced pressure. This gives 28.2 g (71%) of a viscous oil which crystallizes after some time. After cooling to −10° C. the resulting mixture is stirred at −10° C. for 2 hours and at room temperature for one hour With ice-cooling the reaction mixture is stirred at room temperature for 15 minutes The aqueous phase is evaporated to dryness the residue is triturated with acetone the mother liquor is filtered off with suction removal of the solvent the residue is chromatographed The resulting product is dissolved in 3N aqueous sodium hydroxide solution the resulting solution is evaporated to dryness again evaporated to dryness The residue is triturated with acetone the precipitated solid is filtered off with suction the solvent is removed under reduced pressure This gives 28.2 g (71%) of a viscous oil which crystallizes after some time