benzyl (2S)-2-amino-4-methylpentanoate

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

Procedure: To a stirred solution of [4-(3-o-tolyl-ureido)-phenyl]-acetic acid (3.0 g), L-leucine benzyl ester (4.2 g), triethylamine (1.6 ml), and HOBT (1.6 g) in dry DMF (50 ml) at room temperature was added EDCl (2.4 g). After 16 h the mixture was poured into water (400 ml) and extracted with EtOAc (400 ml×2). The combined organics were washed with 5% citric acid (100 ml); saturated NaHCO3 (100 ml); water (100 ml), brine (100 ml); dried over MgSO4; filtered, and concentrated under reduced pressure to about 100 ml. The resulting suspension was filtered to give 4.0 g of the title compound as a white solid. MS [M+1]+ 488.2; 1H nmr (400 MHz, DMSO-d6) δ0.79 (d, J=6.4 Hz, 3H), 0.86 (d, J=6.4 Hz, 3H), 1.45-1.63 (m, 3H), 2.21 (s, 3H), 3.37 (s, 2H), 4.26-4.31 (m, 1H), 5.07 (s, 2H), 6.91 (t, 1H), 7.09-7.15 (m, 4H), 7.29-7.37 (m, 7H), 7.81 (d, 1H), 7.86 (s, 1H), 8.44 (d, 1H), 8.93 (s, 1H). extracted with EtOAc (400 ml×2) The combined organics were washed with 5% citric acid (100 ml) dried over MgSO4 filtered concentrated under reduced pressure to about 100 ml The resulting suspension was filtered

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

Procedure: 4-(Pivaloyloxymethoxycarbonyl)-2,4-(R*,R*)-dibenzylbutyryl chloride (1.2 g) in 10 ml of methylene chloride is added slowly to a solution of 0.60 g of (L)-leucine benzyl ester and 0.30 ml of triethylamine in 20 ml of methylene chloride. The reaction is stirred overnight at room temperature. The solution is washed with 2N hydrochloric acid, then with saturated sodium bicarbonate, dried over magnesium sulfate, filtered and concentrated to give N-[4-pivaloyloxymethoxycarbonyl-(R*,R*)-2,4-dibenzylbutyryl]-L-leucine benzyl ester. The solution is washed with 2N hydrochloric acid with saturated sodium bicarbonate, dried over magnesium sulfate filtered concentrated

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

Procedure: A solution of 19.5 parts N-t-butoxycarbonylglycine 2,4,5-trichlorophenyl ester and 11.1 parts L-leucine benzyl ester in 200 parts methylene chloride is stirred overnight at room temperature. The solvent is then removed by evaporation under reduced pressure. The crude dipeptide is then subjected to low-pressure column chromatography on silica gel to afford N-t-butoxycarbonylglycyl-L-leucine benzyl ester. The solvent is then removed by evaporation under reduced pressure

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

Procedure: Amino acid analysis (after hydrolyzed in 6 N--HCl at 110° C. for 24 hours) (Parenthesized are the theoretical data.): Lys 0.84 (1); Glu 1.02 (1); Leu 1.00 (1); Tyr 0.92 (1).

Conditions: temp:-10.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of triphosgene (15.7 g, 52.9 mmol) in CH2Cl2 (600 mL) was cooled to −10° C. under a nitrogen atmosphere. The solution was treated dropwise with a solution of (S)-2-amino-4-methyl-pentanoic acid benzyl ester (28.1 g, 0.127 mol) and pyridine (26 mL, 0.32 mol) in 150 mL of CH2Cl2. The resulting solution was stirred at −10° C. for 90 minutes and then treated with a solution of hexamethyleneimine (22 mL, 0.38 mmol) in 75 mL of CH2Cl2. The resulting solution was stirred for 48 hours at room temperature. The reaction mixture was concentrated, and the residue was dissolved in ether and washed with 1N HCl solution, water, and saturated aqueous CuSO4 solution. The organic layer was dried (Mg2SO4), treated with activated charcoal, and filtered. The filtrate was concentrated to approximately ½ volume and treated with hexane. The resulting suspension was stored overnight at −10° C. The solid was collected by filtration, washed with hexane, and dried under vacuum to give (S)-2-[(azepane-1-carbonyl)-amino]-4-methyl-pentanoic acid benzyl ester as a white solid (38.6 g, 88%); mp 87-88° C. The resulting solution was stirred for 48 hours at room temperature The reaction mixture was concentrated the residue was dissolved in ether washed with 1N HCl solution, water, and saturated aqueous CuSO4 solution The organic layer was dried (Mg2SO4) treated with activated charcoal filtered The filtrate was concentrated to approximately ½ volume treated with hexane The resulting suspension was stored overnight at −10° C The solid was collected by filtration washed with hexane dried under vacuum

Conditions: temp:-10.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of triphosgene (15.7 g, 52.9 mmol) in CH2Cl2 (600 mL) was cooled to −10° C. under a nitrogen atmosphere. The solution was treated dropwise with a solution of (S)-2-amino-4-methyl-pentanoic acid benzyl ester (28.1 g, 0.127 mol) and pyridine (26 mL, 0.32 mol) in 150 mL of CH2Cl2. The resulting solution was stirred at −10° C. for 90 minutes and then treated with a solution of hexamethyleneimine (22 mL, 0.38 mmol) in 75 mL of CH2Cl2. The resulting solution was stirred for 48 hours at room temperature. The reaction mixture was concentrated, and the residue was dissolved in ether and washed with 1N HCl solution, water, and saturated aqueous CuSO4 solution. The organic layer was dried (Mg2SO4), treated with activated charcoal, and filtered. The filtrate was concentrated to approximately ½ volume and treated with hexane. The resulting suspension was stored overnight at −10° C. The solid was collected by filtration, washed with hexane, and dried under vacuum to give (S)-2-[(azepane-1-carbonyl)-amino]-4-methyl-pentanoic acid benzyl ester as a white solid (38.6 g, 88%); mp 87-88° C. The resulting solution was stirred for 48 hours at room temperature The reaction mixture was concentrated the residue was dissolved in ether washed with 1N HCl solution, water, and saturated aqueous CuSO4 solution The organic layer was dried (Mg2SO4) treated with activated charcoal filtered The filtrate was concentrated to approximately ½ volume treated with hexane The resulting suspension was stored overnight at −10° C The solid was collected by filtration washed with hexane dried under vacuum

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

Procedure: To a stirred solution of [4-(3-o-tolyl-ureido)-phenyl]-acetic acid (3.0 g), L-leucine benzyl ester (4.2 g), triethylamine (1.6 ml), and HOBT (1.6 g) in dry DMF (50 ml) at room temperature was added EDCI (2.4 g). After 16 h the mixture was poured into water (400 ml) and extracted with EtOAc (400 ml×2). The combined organics were washed with 5% citric acid (100 ml); saturated NaHCO3 (100 ml); water (100 ml), brine (100 ml); dried over MgSO4; filtered, and concentrated under reduced pressure to about 100 ml. The resulting suspension was filtered to give 4.0 g of the title compound as a white solid. MS [M+1]+488.2; 1H nmr (400 MHz, DMSO-d6) δ0.79 (d, J=6.4 Hz, 3H), 0.86 (d, J=6.4 Hz, 3H), 1.45-1.63 (m, 3H), 2.21 (s, 3H), 3.37 (s, 2H), 4.26-4.31 (m, 1H), 5.07 (s, 2H), 6.91 (t, 1H), 7.09-7.15 (m, 4H), 7.29-7.37 (m, 7H), 7.81 (d, 1H), 7.86 (s, 1H), 8.44 (d, 1H), 8.93 (s, 1H). extracted with EtOAc (400 ml×2) The combined organics were washed with 5% citric acid (100 ml) dried over MgSO4 filtered concentrated under reduced pressure to about 100 ml The resulting suspension was filtered

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

Procedure: To a stirred solution of [4-(3-o-tolyl-ureido)-phenyl]-acetic acid (3.0 g), L-leucine benzyl ester (4.2 g), triethylamine (1.6 ml), and HOBT (1.6 g) in dry DMF (50 ml) at room temperature was added EDCI (2.4 g). After 16 h the mixture was poured into water (400 ml) and extracted with EtOAc (400 ml×2). The combined organics were washed with 5% citric acid (100 ml); saturated NaHCO3 (100 ml); water (100 ml), brine (100 ml); dried over MgSO4; filtered, and concentrated under reduced pressure to about 100 ml. The resulting suspension was filtered to give 4.0 g of the title compound as a white solid. MS [M+1]+488.2; 1H nmr (400 MHz, DMSO-d6) δ0.79 (d, J=6.4 Hz, 3H), 0.86 (d, J=6.4 Hz, 3H), 1.45-1.63 (m, 3H), 2.21 (s, 3H), 3.37 (s, 2H), 4.26-4.31 (m, 1H), 5.07 (s, 2H), 6.91 (t, 1H), 7.09-7.15 (m, 4H), 7.29-7.37 (m, 7H), 7.81 (d, 1H), 7.86 (s, 1H), 8.44 (d, 1H), 8.93 (s, 1H). extracted with EtOAc (400 ml×2) The combined organics were washed with 5% citric acid (100 ml) dried over MgSO4 filtered concentrated under reduced pressure to about 100 ml The resulting suspension was filtered

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

Procedure: To a solution of L-Leucine benzylester (2.81 g, 12.7 mmol) in tetrahydrofuran (6 mL), 1,4-dioxane (6 mL) and MeOH (6 mL) was added 1,3-propane sultone (1.40 g, 11.5 mmol). The solution was stirred at reflux for 2.5 hours. The reaction mixture was cooled to room temperature. The solid was filtered and washed with acetone (2×20 mL). The filtrate was evaporated under reduced pressure. The residue was dissolved in acetone (20 mL). The product was precipitated with Et2O (200 mL). The solid material was filtered. Both solids were combined and dissolved in 50% EtOH/water (200 mL). Dowex Marathon C ion exchange resin (strongly acidic) was added to the solution. The suspension was stirred for 15 minutes before the resin was removed by filtration. The filtrate was evaporated under reduced pressure and lyophilized, affording the title compound (1.87 g, 47%). 1H NMR (DMSO, 500 MHz) δ ppm 9.34 (s (broad), 1H), 7.39 (m, 5H), 5.25 (s, 2H), 4.10 (m, 1H), 3.09 (m, 2H), 2.60 (m, 2H), 1.95 (m, 2H), 1.64 (m, 3H), 0.86 (m, 6H). 13C (DMSO, 125 MHz) δ ppm 168.90, 134.91, 128.53, 128.50, 128.41, 67.38, 57.37, 49.17, 45.79, 38.06, 24.07, 22.79, 21.78, 21.33. [α]D=+1.8° (c=0.0017 in water), ES-MS 344 (M+1). at reflux for 2.5 hours The solid was filtered washed with acetone (2×20 mL) The filtrate was evaporated under reduced pressure The residue was dissolved in acetone (20 mL) The product was precipitated with Et2O (200 mL) The solid material was filtered dissolved in 50% EtOH/water (200 mL) Dowex Marathon C ion exchange resin (strongly acidic) was added to the solution The suspension was stirred for 15 minutes before the resin was removed by filtration The filtrate was evaporated under reduced pressure

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

Procedure: A solution Of L-leucine benzyl ester tosylate (5.8 g, 14.8 mmol) in 80 mL methylene chloride was stirred together with aqueous solution of saturated sodium bicarbonate (large excess) for I5 min at room temperature. The organic phase was separated, dried over magnesium sulfate and charged with 9-fluorenemethoxycarbonyl-O-succinimide (2.5 g, 7.4 mmol) at room temperature. The reaction was monitored via TLC (silica, 25% EtOAc in hexane). After two hours the reaction was over (according to its TLC with 25% EtOAc in hexane). However it was further stirred at room temperature for 48 hours. The solution was diluted with EtOAc then was washed with water (×2), 3% aqueous HCl, water (×3) and brine. The solution was dried over magnesium sulfate and evaporated. The resulting oil was crystallized from hexane:ether to yield 2.2 g (48.7%) of colorless solid, mp 91°-2° C. The organic phase was separated dried over magnesium sulfate then was washed with water (×2), 3% aqueous HCl, water (×3) and brine The solution was dried over magnesium sulfate evaporated The resulting oil was crystallized from hexane

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

Procedure: 19.9 g (92 mmols) of BOC-Val-OH are dissolved in 200 ml of freshly distilled dimethylformamide, while heating. After cooling to 0°C, 25.9 ml of absolute triethylamine are added and the solution cooled to -10°C before 8.64 ml of chlorocarbonic acid ethyl ester are added. After 10 minutes, a solution of 23.2 g (90 mmols) of H-Leu-OBzl, HCL in 90 ml of dimethylformamide is added at -10°C. The mixture is allowed to stand at -10°C for 30 minutes, at 0°C for 3 hours, and at 20°C for 16 hours. Undissolved matter is then filtered off and the filtrate concentrated to dryness under a high vacuum. The residue is dissolved in ethyl acetate and the solution washed with dilute citric acid solution, water, sodium bicarbonate solution, and water, dried with sodium sulfate, and evaporated. On addition of petroleum ether the product crystallizes overnight. Melting point 88.5° - 89.5°C; [α]D20 -22° (c = 2 in dimethylformamide); Rf2 = 0.73. while heating are added to stand at -10°C for 30 minutes, at 0°C for 3 hours at 20°C for 16 hours Undissolved matter is then filtered off the filtrate concentrated to dryness under a high vacuum The residue is dissolved in ethyl acetate the solution washed with dilute citric acid solution, water, sodium bicarbonate solution, and water dried with sodium sulfate evaporated On addition of petroleum ether the product crystallizes overnight

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

Procedure: 19.9 g (92 mmols) of BOC-Val-OH are dissolved in 200 ml of freshly distilled dimethylformamide, while heating. After cooling to 0°C, 25.9 ml of absolute triethylamine are added and the solution cooled to -10°C before 8.64 ml of chlorocarbonic acid ethyl ester are added. After 10 minutes, a solution of 23.2 g (90 mmols) of H-Leu-OBzl, HCL in 90 ml of dimethylformamide is added at -10°C. The mixture is allowed to stand at -10°C for 30 minutes, at 0°C for 3 hours, and at 20°C for 16 hours. Undissolved matter is then filtered off and the filtrate concentrated to dryness under a high vacuum. The residue is dissolved in ethyl acetate and the solution washed with dilute citric acid solution, water, sodium bicarbonate solution, and water, dried with sodium sulfate, and evaporated. On addition of petroleum ether the product crystallizes overnight. Melting point 88.5° - 89.5°C; [α]D20 -22° (c = 2 in dimethylformamide); Rf2 = 0.73. while heating are added to stand at -10°C for 30 minutes, at 0°C for 3 hours at 20°C for 16 hours Undissolved matter is then filtered off the filtrate concentrated to dryness under a high vacuum The residue is dissolved in ethyl acetate the solution washed with dilute citric acid solution, water, sodium bicarbonate solution, and water dried with sodium sulfate evaporated On addition of petroleum ether the product crystallizes overnight