L-(+)-Cysteine → HCID 54452303, compound

Participants

Reaction Steps

Treat the product of Step B (12.5 g) in EtOH (400 mL) with papain (2.56 g freshly ground), L-cysteine (0.156 g) and freshly made 1M citrate buffer pH 4.5 (2.8 mL). After 2 hr, add papain (1.28 g), L-cysteine (0.078 g), and 1M citrate buffer pH 4.5 (1.4 mL). Repeat the latter addition of papain, L-cystein, and citrate buffer at 4 and 6 hr intervals. Stir the resulting mixture for 4 days. Filter, wash with EtOH, and concentrate in vacuo to a residue. Partition the residue between Et2O (1400 mL)/5% NaHCO3 (6×150 mL). Concentrate the dried (MgSO4) Et2O solution in vacuo to give N-benzyloxycarbonyl-3-methanesulfonamido-L-phenylalanine ethyl ester, [α]26D =-6.7° (MeOH).

Provenance & Evidence