Diisopropylcarbodiimide → (S)-2-Mercapto-3-methylbutyroyl-(L)-homo-phenylalanyl-(L)-phenylalanine

Beteiligte Stoffe

Reaktionsschritte

Combine Fmoc-(L)-phenylalanine-NovaSyn® TGT resin (1.0 g, 0.15 mmol/g, Nova Biochem), dimethylformamide (3 mL) and 50% piperidine/dimethylformamide (3 mL). After 5 minutes, filter, add dimethylformamide (3 mL) and 50% piperidine/dimethylformamide (3 mL), bubble for 10 minutes, and filter. Rinse the resin with dimethylformamide (10 times 5 mL), dichloromethane (3 times 5 mL), and then dimethylformamide (5 mL). Kaiser (ninhydrin) test indicates complete deprotection. Add Fmoc-(L)-homophenylalanine (0.240 g, 0.5 mmol), O-(7-azabenzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (0.228 g, 0.60 mmol), and N,N-diisopropylethylamine (0.21 mL, 1.20 mmol), and dimethylformamide (5 mL). After 15 hours, filter, rinse the resin with dimethylformamide (9 times 5 mL), dichloromethane (3 times 5 mL), and then dimethylformamide (5 mL). Add dimethylformamide (3 mL) and 50% piperidine/dimethylformamide (3 mL), bubble for 10 minutes, and filter. Rinse the resin with dimethylformamide (10 times 5 mL), dichloromethane (3 times 5 mL), and then dimethylformamide (5 mL). Kaiser (ninhydrin) test indicates complete deprotection. Add (R)-2-bromo-3-methylbutyric acid (0.145 g, 0.6 mmol), 1,3-diisopropylcarbodiimide (0.076 g, 0.60 mmol), and N,N-diisopropylethylamine (0.21 mL, 1.20 mmol) in N-methylpyrrolidinone (5 mL). After 15 hours, filter, rinse the resin with dimethylformamide (9 times 5 mL), dichloromethane (3 times 5 mL), and then dimethylformamide (5 mL). Combine the resin with a degassed solution of potassium thioacetate (0.137 g, 1.2 mmol) in N-methylpyrolidinone (5 mL). After 3 hours, filter and rinse the resin with dimethylformamide (9 times 5 mL). Combine the resin with a degassed saturated methanolic ammonia solution (5 mL). After 5 minutes, filter and rinse the resin with methanol (5 times 5 mL). Combine the resin and a degassed 95% trifluoroacetic acid/4% water/1% 2-mercaptoethanol solution (10 mL). After 3 hours, filter, rinse with 50% trifluoroacetic acid/dichloromethane (2 times 10 mL). Concentrate the filtrate in vacuo to give a residue. Combine the residue with 1% trifluoroacetic acid/acetonitrile solution and evaporate under a stream of nitrogen to give a residue. Combine the residue and water (about 4 mL) and lyophilize to give a residue. Combine the residue and acetonitrile and water and again lyophilize to give a residue. Purify by HPLC to give the title compound: retention time=4:24 minutes, YMC Inc. 4.0 mm×50 mm ODS-A column, flow rate 1.0 mL/minute, initial conditions 70% A (95% water/5% acetonitrile/0.1% trifluoroacetic acid) and 30% B (5% water/95% acetonitrile/0.085% trifluoracetic acid) and a linear gradient over 5 minutes to 100% B. Mass Spectrum (MH+=443).

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