dimethyl (2S)-2-aminobutanedioate

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

Procedure: Following the procedures outlined in Example 34, substituting 3-(6,8-dichloro-2-methyl-1,2,3,4-tetrahydroisoquinolin-4-yl)aniline (intermediate 31.5) for 4-(6,8-dichloro-2-methyl-1,2,3,4-tetrahydroisoquinolin-4-yl)aniline and (S)-diethyl 2-aminopentanedioate for (S)-dimethyl 2-aminosuccinate gave, after purification by preparative HPLC, the title compound as a TFA salt. 1H-NMR (300 MHz, DMSO-d6, ppm): δ 8.74 (s, 1H), 7.67 (s, 1H), 7.42 (m, 1H), 7.27-7.25 (m, 2H), 6.79 (m, 2H), 6.52-6.49 (m, 1H), 4.63-4.58 (m, 1H), 4.44 (m, 2H), 4.20-4.16 (m, 1H), 3.72-3.64 (m, 2H), 2.99 (s, 3H), 2.34-2.27 (m, 2H), 2.01-1.97 (m, 2H), 1.82-1.77 (m, 2H). MS 480 [M+H]+. gave after purification by preparative HPLC

Conditions: temp:2.51; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Into a 50-mL 3-necked round-bottom flask purged and maintained with an inert atmosphere of nitrogen, was placed a solution of 4-(6,8-dichloro-2-methyl-1,2,3,4-tetrahydroisoquinolin-4-yl)benzenamine (intermediate 30.7) (200 mg, 0.65 mmol, 1.00 equiv) in dichloromethane (10 mL), triethylamine (1.2 mL). This was followed by the addition of bis(trichloromethyl) carbonate (200 mg, 0.67 mmol, 1.03 equiv) slowly with stirring at 0-5° C. The resulting solution was stirred for 1 h at room temperature. To this was added triethylamine (1 mL) followed by (S)-dimethyl 2-aminosuccinate (200 mg, 1.24 mmol, 1.91 equiv) in several batches. The resulting solution was stirred for 2 h at room temperature. The resulting mixture was concentrated under vacuum and the residue was applied onto a silica gel column and eluted with ethyl acetate/petroleum ether (1:10-1:5). This resulted in 50 mg (15%) of (2S)-dimethyl 2-(3-(4-(6,8-dichloro-2-methyl-1,2,3,4-tetrahydroisoquinolin-4-yl)phenyl)ureido)succinate as yellow oil. Into a 50-mL 3-necked round-bottom flask purged maintained with an inert atmosphere of nitrogen The resulting solution was stirred for 1 h at room temperature The resulting solution was stirred for 2 h at room temperature The resulting mixture was concentrated under vacuum eluted with ethyl acetate/petroleum ether (1:10-1:5) This resulted in 50 mg (15%) of (2S)-dimethyl 2-(3-(4-(6,8-dichloro-2-methyl-1,2,3,4-tetrahydroisoquinolin-4-yl)phenyl)ureido)succinate as yellow oil

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

Procedure: The present inventors have further found that 5-benzyl-3,6-dioxo-2-piperazine acetic acid methyl ester is also obtained by condensating and cyclizing the N-carboxylic acid anhydride of L-phenylalanine and L-aspartic acid dimethyl ester in an organic solvent, and 5-benzyl-3,6-dioxo-2-piperazine acetic acid is obtained by hydrolyzing 5-benzyl-3,6-dioxo-2-piperazine acetic acid methyl ester with an alkali, if necessary. is also obtained

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

Procedure: The present inventors have further found that 5-benzyl-3,6-dioxo-2-piperazine acetic acid methyl ester is also obtained by condensating and cyclizing the N-carboxylic acid anhydride of L-phenylalanine and L-aspartic acid dimethyl ester in an organic solvent, and 5-benzyl-3,6-dioxo-2-piperazine acetic acid is obtained by hydrolyzing 5-benzyl-3,6-dioxo-2-piperazine acetic acid methyl ester with an alkali, if necessary. is also obtained

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

Procedure: Following the procedures outlined in Example 34, substituting 3-(6,8-dichloro-2-methyl-1,2,3,4-tetrahydroisoquinolin-4-yl)aniline (intermediate 31.5) for 4-(6,8-dichloro-2-methyl-1,2,3,4-tetrahydroisoquinolin-4-yl)aniline and (S)-diethyl 2-aminopentanedioate for (S)-dimethyl 2-aminosuccinate gave, after purification by preparative HPLC, the title compound as a TFA salt. 1H-NMR (300 MHz, DMSO-d6, ppm): δ 8.74 (s, 1H), 7.67 (s, 1H), 7.42 (m, 1H), 7.27-7.25 (m, 2H), 6.79 (m, 2H), 6.52-6.49 (m, 1H), 4.63-4.58 (m, 1H), 4.44 (m, 2H), 4.20-4.16 (m, 1H), 3.72-3.64 (m, 2H), 2.99 (s, 3H), 2.34-2.27 (m, 2H), 2.01-1.97 (m, 2H), 1.82-1.77 (m, 2H). MS 480 [M+H]+. gave after purification by preparative HPLC

Conditions: temp:2.51; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Into a 50-mL 3-necked round-bottom flask purged and maintained with an inert atmosphere of nitrogen, was placed a solution of 4-(6,8-dichloro-2-methyl-1,2,3,4-tetrahydroisoquinolin-4-yl)benzenamine (intermediate 30.7) (200 mg, 0.65 mmol, 1.00 equiv) in dichloromethane (10 mL), triethylamine (1.2 mL). This was followed by the addition of bis(trichloromethyl) carbonate (200 mg, 0.67 mmol, 1.03 equiv) slowly with stirring at 0-5° C. The resulting solution was stirred for 1 h at room temperature. To this was added triethylamine (1 mL) followed by (S)-dimethyl 2-aminosuccinate (200 mg, 1.24 mmol, 1.91 equiv) in several batches. The resulting solution was stirred for 2 h at room temperature. The resulting mixture was concentrated under vacuum and the residue was applied onto a silica gel column and eltued with ethyl acetate/petroleum ether (1:10-1:5). This resulted in 50 mg (15%) of (2S)-dimethyl 2-(3-(4-(6,8-dichloro-2-methyl-1,2,3,4-tetrahydroisoquinolin-4-yl)phenyl)ureido)succinate as yellow oil. Into a 50-mL 3-necked round-bottom flask purged maintained with an inert atmosphere of nitrogen The resulting solution was stirred for 1 h at room temperature The resulting solution was stirred for 2 h at room temperature The resulting mixture was concentrated under vacuum This resulted in 50 mg (15%) of (2S)-dimethyl 2-(3-(4-(6,8-dichloro-2-methyl-1,2,3,4-tetrahydroisoquinolin-4-yl)phenyl)ureido)succinate as yellow oil

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

Procedure: Following the procedures outlined in Example 34, substituting 3-(6,8-dichloro-2-methyl-1,2,3,4-tetrahydroisoquinolin-4-yl)aniline (intermediate 31.5) for 4-(6,8-dichloro-2-methyl-1,2,3,4-tetrahydroisoquinolin-4-yl)aniline and (S)-diethyl 2-aminopentanedioate for (S)-dimethyl 2-aminosuccinate gave, after purification by preparative HPLC, the title compound as a TFA salt. 1H-NMR (300 MHz, DMSO-d6, ppm): δ 8.74 (s, 1H), 7.67 (s, 1H), 7.42 (m, 1H), 7.27-7.25 (m, 2H), 6.79 (m, 2H), 6.52-6.49 (m, 1H), 4.63-4.58 (m, 1H), 4.44 (m, 2H), 4.20-4.16 (m, 1H), 3.72-3.64 (m, 2H), 2.99 (s, 3H), 2.34-2.27 (m, 2H), 2.01-1.97 (m, 2H), 1.82-1.77 (m, 2H). MS 480 [M+H]+. gave after purification by preparative HPLC

Conditions: temp:2.51; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Into a 50-mL 3-necked round-bottom flask purged and maintained with an inert atmosphere of nitrogen, was placed a solution of 4-(6,8-dichloro-2-methyl-1,2,3,4-tetrahydroisoquinolin-4-yl)benzenamine (intermediate 30.7) (200 mg, 0.65 mmol, 1.00 equiv) in dichloromethane (10 mL), triethylamine (1.2 mL). This was followed by the addition of bis(trichloromethyl) carbonate (200 mg, 0.67 mmol, 1.03 equiv) slowly with stirring at 0-5° C. The resulting solution was stirred for 1 h at room temperature. To this was added triethylamine (1 mL) followed by (S)-dimethyl 2-aminosuccinate (200 mg, 1.24 mmol, 1.91 equiv) in several batches. The resulting solution was stirred for 2 h at room temperature. The resulting mixture was concentrated under vacuum and the residue was applied onto a silica gel column and eltued with ethyl acetate/petroleum ether (1:10-1:5). This resulted in 50 mg (15%) of (2S)-dimethyl 2-(3-(4-(6,8-dichloro-2-methyl-1,2,3,4-tetrahydroisoquinolin-4-yl)phenyl)ureido)succinate as yellow oil. Into a 50-mL 3-necked round-bottom flask purged maintained with an inert atmosphere of nitrogen The resulting solution was stirred for 1 h at room temperature The resulting solution was stirred for 2 h at room temperature The resulting mixture was concentrated under vacuum This resulted in 50 mg (15%) of (2S)-dimethyl 2-(3-(4-(6,8-dichloro-2-methyl-1,2,3,4-tetrahydroisoquinolin-4-yl)phenyl)ureido)succinate as yellow oil

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

Procedure: Diethylaspartate hydrochloride (3, 85.31 g, 0.432 mol) was dissolved in a saturated solution of aqueous sodium carbonate (200 mL) and extracted with ethyl acetate (10×250 mL) in a separatory funnel. The combined organic phases were dried by filtration through magnesium sulfate and sodium sulfate and concentrated in vacuo to provide dimethyl aspartate (58.73 g, 0.364 mol, 84%) as a pale yellow oil. This material provided satisfactory 1H NMR data and was used immediately in the preparation of N-benzyloxycarbonylglycyl-L-α-aspartic acid dimethyl ester (5). extracted with ethyl acetate (10×250 mL) in a separatory funnel The combined organic phases were dried by filtration through magnesium sulfate and sodium sulfate concentrated in vacuo

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

Procedure: An example of the use of the novel N-protected-α-amino acid compounds of this invention in peptide synthesis is the preparation of α-aspartyl-phenylalanine methyl ester, a known sweetening agent. The dipeptide is conveniently prepared by coupling N-(1-methylcyclobutyloxycarbonyl) aspartic anhydride with phenylalanine methyl ester hydrochloride. Introduction of the N-(1-methylcyclobutyloxycarbonyl blocking group into aspartic acid is accomplished by reacting 1-methylcyclobutylchloroformate with aspartic acid dimethyl ester in accordance with the process of this invention. Equimolar quantities of the chloroformate and aspartic acid dimethyl ester are reacted in chloroform at 0°C. at pH 8. Reaction is carried out by portion-wise addition of 1-methylcyclobutyl chloroformate to the aspartic acid suspended in chloroform. Triethylamine is added to the reaction during the addition to maintain pH 8. After allowing the reaction to run to completion at room temperature, the reaction mixture is treated according to the procedure outlined above to afford the N-(1-methylcyclobutyloxycarbonyl) aspartic acid dimethyl ester. The free acid is obtained by saponifying the ester in a basic aqueous methanol solution. After acidifying the reaction mixture with sulfuric acid, the N-(1-methylcyclobutyloxycarbonyl) aspartic acid is isolated by extraction. Reaction to maintain pH 8 the reaction to run to completion at room temperature the reaction mixture is treated

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

Procedure: In like manner, but using dimethyl aspartate and dimethyl glutamate in place of diethyl malonate affords the corresponding N-[3β-hydroxy-11-oxo-18β-olean-12-en-30-oyl]aspartic acid and glutamic acid compounds which are converted to their disodium salts according to Example I-C.

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

Procedure: Following the procedures outlined in Example 34, substituting 3-(6,8-dichloro-2-methyl-1,2,3,4-tetrahydroisoquinolin-4-yl)aniline (intermediate 31.5) for 4-(6,8-dichloro-2-methyl-1,2,3,4-tetrahydroisoquinolin-4-yl)aniline and (S)-diethyl 2-aminopentanedioate for (S)-dimethyl 2-aminosuccinate gave, after purification by preparative HPLC, the title compound as a TFA salt. 1H-NMR (300 MHz, DMSO-d6, ppm): δ 8.74 (s, 1H), 7.67 (s, 1H), 7.42 (m, 1H), 7.27-7.25 (m, 2H), 6.79 (m, 2H), 6.52-6.49 (m, 1H), 4.63-4.58 (m, 1H), 4.44 (m, 2H), 4.20-4.16 (m, 1H), 3.72-3.64 (m, 2H), 2.99 (s, 3H), 2.34-2.27 (m, 2H), 2.01-1.97 (m, 2H), 1.82-1.77 (m, 2H). MS 480 [M+H]+. gave after purification by preparative HPLC