1: With hydrogenchloride; water T=20 - 30°C; 10 h; 2: With potassium phosphate in toluene T=35°C; pH=> 10; 3: With formic acid; triethylamine; (CH3C6H4CH(CH3)2)RuCl(NH2CH(C6H5)CH(C6H5)NSO2C6H2(CH(CH3)2)3) in toluene; acetonitrile T=-5°C; 24 h; Inert atmosphere;

triethanolamine; sitagliptin transaminase CDX-017; pyridoxal 5'-phosphate; N-isopropylamine hydrochloride in water; dimethyl sulfoxide T=40°C; pH=8.5; Inert atmosphere; enantioselective reaction;

triethanolamine; sitagliptin transaminase CDX-017; pyridoxal 5'-phosphate; N-isopropylamine hydrochloride in water; dimethyl sulfoxide T=40°C; pH=9.5; Inert atmosphere; enantioselective reaction;

triethanolamine; sitagliptin transaminase CDX-017; pyridoxal 5'-phosphate; N-isopropylamine hydrochloride in water; dimethyl sulfoxide T=40°C; pH=8.5; Inert atmosphere; optical yield given as percent eeenantioselective reaction;

1: acetonitrile / Inert atmosphere 2: sodium hydroxide / N,N-dimethyl-formamide / 6 h / Inert atmosphere 3: triethylamine / isopropanol acetate / 1.25 h / 0 - 10 °C / Inert atmosphere 4: sitagliptin transaminase CDX-017; triethanolamine; pyridoxal 5'-phosphate; N-isopropylamine hydrochloride / water; dimethyl sulfoxide / 40 °C / pH 9.5 / Inert atmosphere View Scheme

1: sodium hydroxide / N,N-dimethyl-formamide / 6 h / Inert atmosphere 2: triethylamine / isopropanol acetate / 1.25 h / 0 - 10 °C / Inert atmosphere 3: sitagliptin transaminase CDX-017; triethanolamine; pyridoxal 5'-phosphate; N-isopropylamine hydrochloride / water; dimethyl sulfoxide / 40 °C / pH 9.5 / Inert atmosphere View Scheme

1.1: toluene-4-sulfonic acid / tetrahydrofuran / 60 °C / Inert atmosphere 2.1: lithium hexamethyldisilazane / tetrahydrofuran / 2.83 h / -25 - -15 °C / Inert atmosphere 2.2: 3.33 h / -20 - -15 °C / Inert atmosphere 3.1: acetonitrile / Inert atmosphere 4.1: 1,8-diazabicyclo[5.4.0]undec-7-ene / acetonitrile / 23 °C / Inert atmosphere 5.1: triethylamine / isopropanol acetate / 1.25 h / 0 - 10 °C / Inert atmosphere 6.1: sitagliptin transaminase CDX-017; triethanolamine; pyridoxal 5'-phosphate; N-isopropylamine hydrochloride / water; dimethyl sulfoxide / 40 °C / pH 9.5 / Inert atmosphere View Scheme

1.1: lithium hexamethyldisilazane / tetrahydrofuran / 2.83 h / -25 - -15 °C / Inert atmosphere 1.2: 3.33 h / -20 - -15 °C / Inert atmosphere 2.1: acetonitrile / Inert atmosphere 3.1: 1,8-diazabicyclo[5.4.0]undec-7-ene / acetonitrile / 23 °C / Inert atmosphere 4.1: triethylamine / isopropanol acetate / 1.25 h / 0 - 10 °C / Inert atmosphere 5.1: sitagliptin transaminase CDX-017; triethanolamine; pyridoxal 5'-phosphate; N-isopropylamine hydrochloride / water; dimethyl sulfoxide / 40 °C / pH 9.5 / Inert atmosphere View Scheme

1: triethylamine / isopropanol acetate / 1.25 h / 0 - 10 °C / Inert atmosphere 2: sitagliptin transaminase CDX-017; triethanolamine; pyridoxal 5'-phosphate; N-isopropylamine hydrochloride / water; dimethyl sulfoxide / 40 °C / pH 9.5 / Inert atmosphere View Scheme

1.1: water; methanol / 0 - 5 °C / Industry scale 2.1: oxalyl dichloride / N,N-dimethyl-formamide / dichloromethane / 1.75 h / 25 °C / Industry scale 2.2: 2.5 h / 10 - 20 °C 2.3: 10 h / 20 °C 3.1: hydrogenchloride; water / 10 h / 20 - 30 °C 3.2: 35 °C / pH > 10 3.3: 24 h / -5 °C / Inert atmosphere View Scheme