4-Methylmorpholine → (R)-3-mercapto-2-[(S)-2-methyl-3-trityloxy-propionylamino]-propionic acid methyl ester

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Reaction Steps

To a suspension of 9.97 g of (S)-2-trityloxy-propionic acid, 5.60 g of L-cysteine methyl ester hydrochloride and 6.6 g of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride in 50 ml acetonitrile was added over 10 min a solution of 6.9 g of 4-methyl-morpholine in 50 ml of acetonitrile. The mixture was stirred at room temperature for 3 h and then partitioned between water and ethyl acetate. The organic layer was washed with brine, dried over magnesium sulfate and evaporated in vacuo. The residue was chromatographed on silica gel using ethyl acetate/hexane (1:2, v/v) as eluent to yield 2.30 g of (R)-3-mercapto-2-[(S)-2-methyl-3-trityloxy-propionylamino]-propionic acid methyl ester as amorphous solid. 1H-NMR (250 MHz,DMSO-d6): δ0.88(d,J=10 Hz,3H); 2.42(t,J=15 Hz, 1H); 2.78 (dd,J=10 Hz and 15 Hz,2H); 3.66(s,3H); 4.01(q,J=10 Hz, 1H); 4.20-4.30(m, 1H); 7.25-7.50(m, 16H); 7.82(d,J=16 Hz,1H) ppm.

Provenance & Evidence