(2S)-2-amino-4-methyl-N-phenylpentanamide

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

Procedure: The crude carboxylic acid (45 mg, 0.11 mmol) was dried by evaporation of a toluene solution and then dissolved in DMF (0.40 mL). Molecular sieves (4 Å, 0.16 g) and N-methylmorpholine (0.027 mL, 25 mg, 0.25 mmol) were added. After 10 min., benzotfiazol-1-yloxytris(dimethylamino)phosphonium hexafiuorophosphate (60 mg, 0.14 mmol) was added and the solution was stirred for 40 min. before the addition of L-leucine anilide (28 mg, 0.14 mmol). After 1.5 h at room temperature, the solution was diluted with 20 mL of EtOAc and washed with 2 N aq. HCl (10 mL), saturated aq. NaHCO3 (10 mL), and saturated aq. NaCl (10 mL). The organic layer was dried (Na2SO4), decanted, and evaporated. Purification by flash column chromatography on silica gel (4.7 g) eluting with 100 mL of 3% EtOAc/dichloromethane gave 55 mg (83% yield) of the title compound as a colorless film. NMR (400 MHz, CDCl3) indicated a 1:1 mixture of diastereomers: δ8.50 (s, 1 H), 7.47 (d, 2H, J=7 Hz), 7.38-7.29 (m, 5H), 7.25 (t, 2H, J=7 Hz), 7.06 (t, 1H, J=7 Hz), 7.04 (d, 1H, J=8 Hz), 7.02 (d, 1H, J=8 Hz), 6.96 (d, 1H, J=8 Hz), 6.93 (d, 1H, J=8 Hz), 6.21 (d, 0.5H, J=8 Hz), 6.16 (d, 0.5H, J=8 Hz), 5.11 (s, 2H), 4.66 (bq, 1H, J=7 Hz), 2.95 (quintet, 0.5 H, J=8 Hz), 2.92 (quintet, 0.5H, J=8 Hz), 2.60-2.37 (m, 5H), 2.16-2.06 (m, 1H), 2.00-1.54 (m, 11H), 0.99 (d, 3H, J=6 Hz), 0.97 (d, 1.5H, J=6 Hz), 0.96 (d, 1.5 H, J=6 Hz), 0.93 (t, 1.5H, J=7 Hz), 0.92 (t, 1.5H, J=7 Hz). After 1.5 h at room temperature washed with 2 N aq. HCl (10 mL), saturated aq. NaHCO3 (10 mL), and saturated aq. NaCl (10 mL) The organic layer was dried (Na2SO4) decanted evaporated Purification by flash column chromatography on silica gel (4.7 g) eluting with 100 mL of 3% EtOAc/dichloromethane

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

Procedure: A portion (313 mg) of the crude 2-((hydroxy(methyl)phosphinyl)methyl)-4-phenylbutanoic acid from Step B was dissolved in tetrahydrofuran (3.0 mL) and 4 Å molecular sieves (0.40 g) were added. The mixture was stirred at room temperature and 1,1'-carbonyldiimidazole (215 mg, 1.33 mmol) was added, followed 15 min later by L-leucine N-phenylamide (297 mg, 1.44 mmol).7After 22 h, the mixture was diluted with ethyl acetate (30 mL) and washed with 2N aqueous hydrochloric acid (2×15 mL) and saturated aqueous sodium chloride (15 mL). The organic layer was dried (sodium sulfate) decanted, and evaporated to give 511 mg of colorless foam. The two diastereomers of a portion (145 mg) of the crude product were separated by high pressure liquid chromatography on a 22 mm×25 cm reverse phase column (Whatman ODS-3, Partisil 10) eluting with 60% methanol/40% water/0.05% trifluoroacetic acid (flow rate of 25 mL/min, detection at 250 nm). This yielded the more mobile isomer (43 mg, 31% yield for Steps B-C) and the less mobile isomer (51 mg, 36% yield for Steps B-C), both obtained as brittle films. 4 Å molecular sieves (0.40 g) were added washed with 2N aqueous hydrochloric acid (2×15 mL) and saturated aqueous sodium chloride (15 mL) The organic layer was dried (sodium sulfate) decanted evaporated

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

Procedure: The crude product from Step G was dissolved in tetrahydrofuran (80 mL) and the solution was cooled in an ice bath. A slurry of 1,1'-carbonyldiimidazole (4.09 g, 25.2 mmol) in tetrahydrofuran (10 mL) was added over 10 min with additional tetrahydrofuran (3×5 mL) to complete the transfer. After 30 min, a solution of L-leucine N-phenylamide (5.60 g, 27.1 mmol) in tetrahydrofuran (10 mL) was added over 10 min with additional tetrahydrofuran (5 mL) to complete the transfer. The homogeneous solution was allowed to slowly warm to room temperature and stirred for 16 h. The mixture was concentrated on a rotary evaporator to remove most of the tetrahydrofuran and the residue was partitioned between ethyl acetate (150 mL) and 2N aqueous hydrochloric acid (75 mL). The ethyl acetate layer was washed with saturated aqueous sodium chloride (2×25 mL). The crystals which spontaneously formed in the organic layer were separated by filtration and partioned between chloroform (300 mL) and 2N aqueous hydrochloric acid, and the chlorform layer was washed with saturated aqueous sodium chloride (50 mL). The sodium chloride layer was extracted with chloroform (2×25 mL). The combined chlorform extracts were dried (magnesium sulfate), filtered, and evaporated. The residue was dissolved in boiling tetrahydrofuran (100 mL), allowed to cool to 25° C., evaporated to a mass of 40 g, and dissolved in ethyl acetate (150 mL). After 2 h at 25° C., the crystals were separated by filtration,washed with ethyl acetate (2×20 mL) and ether (20 mL), and dried under vacuum to give 6.17 g of almost colorless crystals. Evaporation of the mother liquor and recrystallization produced a second crop of 1.62 g (total yield 54% for steps F-H) of (2-(((4-(1,3-dihydro-1,3-dioxo-2H-isoindol-2-yl)butyl)hydroxyphosphinyl)methyl)-4-phenylbutanoyl)-L-leucine N-phenylamide. the solution was cooled in an ice bath The mixture was concentrated on a rotary evaporator to remove most of the tetrahydrofuran the residue was partitioned between ethyl acetate (150 mL) and 2N aqueous hydrochloric acid (75 mL) The ethyl acetate layer was washed with saturated aqueous sodium chloride (2×25 mL) The crystals which spontaneously formed in the organic layer were separated by filtration the chlorform layer was washed with saturated aqueous sodium chloride (50 mL) The sodium chloride layer was extracted with chloroform (2×25 mL) The combined chlorform extracts were dried (magnesium sulfate) filtered evaporated The residue was dissolved to cool to 25° C. evaporated to a mass of 40 g dissolved in ethyl acetate (150 mL) After 2 h at 25° C. the crystals were separated by filtration,washed with ethyl acetate (2×20 mL) and ether (20 mL) dried under vacuum to give 6.17 g of almost colorless crystals Evaporation of the mother liquor and recrystallization

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

Procedure: 3.76 g (19.6 mmol) of EDCl was added to 40 ml of THF solution of 1.99 g (9.79 mmol) of Boc-Aib-OH (manufactured by Sigma-Aldrich Corporation), and 2.03 g (9.79 mmol) of H-Leu-NHPh obtained in Synthesis Example 2-2, followed by stirring for 17 hours at room temperature. After a reaction mixture was concentrated under reduced pressure, the concentrate was extracted by adding water and ethyl acetate. After an organic layer was washed sequentially with a diluted hydrochloric acid, an aqueous solution of sodium hydrogen carbonate and water (one time for each), it was concentrated under reduced pressure, thereby obtaining crude amide. The obtained amide compound was purified by a silica gel column chromatography (hexane/ethyl acetate=5/1 to 1/1 (volume ratio)), thereby obtaining 2.42 g of the product with a yield of 63.1%. obtained in Synthesis Example 2-2 After a reaction mixture was concentrated under reduced pressure the concentrate was extracted by adding water and ethyl acetate After an organic layer was washed sequentially with a diluted hydrochloric acid an aqueous solution of sodium hydrogen carbonate and water (one time for each), it was concentrated under reduced pressure obtaining crude amide The obtained amide compound was purified by a silica gel column chromatography (hexane/ethyl acetate=5/1 to 1/1 (volume ratio))