1: acetic acid tert-butyl ester; (1R,3aR,6aS)-octahydrocyclopenta[c]pyrrole-1-carboxylic acid hydrochloride in dichloromethane T=0 - 21°C; 2: With methanesulfonic acid in dichloromethane; water T=0 - 21°C; 18.25 h; Sealed tube; 3: oxalic acid

1: acetic acid tert-butyl ester; (1S,3aR,6aS)-octahydrocyclopenta[c]pyrrole-1-carboxylic acid hydrochloride With methanesulfonic acid in chloroform T=0 - 25°C; 18 h; 2: oxalic acid in isopropyl alcohol T=75 - 80°C; 0.5 h;

1: (S)-1,2,3,4-tetrahydronaphthalen-1-aminium (1S,3aR,6aS)-2-(t-butoxycarbonyl)octahydrocyclopenta[c]pyrrole-1-carboxylate With sodium hydrogen sulphate in tert-butyl methyl ether; water 0.5 h; 2: tert-butyl alcohol With 4-(N,N-dimethlyamino)pyridine; sodium hydrogen sulphate; di-tert-butyl dicarbonate in tert-butyl methyl ether; water T=20 - 25°C; 5 - 6 h; 3: oxalic acid With methanesulfonic acid; potassium carbonate Product distribution / selectivity; more than 3 stages;

1.1: water; hydrogenchloride / methanol / 24 h / |Reflux 2.1: methanesulfonic acid / chloroform / 18 h / 0 - 25 °C 2.2: 0.5 h / 75 - 80 °C View Scheme