1.1: sodium hydroxide; water / methanol / 5 - 10 °C 1.2: pH 2 2.1: N-ethyl-N,N-diisopropylamine / 1-methyl-pyrrolidin-2-one / -25 °C 3.1: hydrogen / palladium on activated charcoal / ethyl acetate; water / 3-(N-morpholino)propanesulfonic acid buffer View Scheme

1: 4-Nitrobenzyl (2S,4S)-4-(acetylthio)-2-[(dimethylamino)carbonyl]pyrrolidine-1-carboxylate With pyrrolidine in N,N-dimethyl-formamide T=-5 - 0°C; 0.5 h; 2: MAP With N-ethyl-N,N-diisopropylamine in N,N-dimethyl-formamide T=-40 - -35°C; 1 h;

1.1: sodium hydroxide; water / methanol / 5 - 10 °C 1.2: pH 2 2.1: N-ethyl-N,N-diisopropylamine / 1-methyl-pyrrolidin-2-one / -25 °C View Scheme

acetyl chloride in methanol T=25 - 30°C; 6 h;