1: N-Boc-4-oxo-L-proline methyl ester With sodium hexamethyldisilazane in tetrahydrofuran T=-78°C; 0.333333 h; 2: N,N-bis(trifluoromethanesulfonyl)aniline in tetrahydrofuran T=-78°C; 3 h;

1: N-Boc-4-oxo-L-proline methyl ester With sodium hexamethyldisilazane in tetrahydrofuran T=-78°C; 0.5 h; 2: N,N-diphenyltrifluoromethanesulfonamide in tetrahydrofuran T=-78°C; 4 h;

lithium hexamethyldisilazane in tetrahydrofuran T=-78 - -20°C;

1: 56 percent / tetrabutylammonium fluoride / 24 h / 0 - 20 °C 2: 94 percent / NaBH4; LiCl / ethanol; tetrahydrofuran / 18 h / 20 °C 3: 89 percent / triethylamine; 4-dimethylaminopyridine / CH2Cl2 / 18 h / 20 °C 4: NaH / tetrahydrofuran / 2 h / 0 - 20 °C 5: potassium tert-butoxide / tetrahydrofuran / 2 h / -40 °C 6: 85 percent / tetrabutylammonium fluoride / tetrahydrofuran / 0.5 h / 20 °C 7: H2 / Raney-Ni / methanol 8: 94 percent / NaOCl; NaClO2; 2,2,6,6-tetramethyl-1-piperidinoxyl / acetonitrile; aq. phosphate buffer / 24 h / 45 °C / pH 6.7 View Scheme

1: 89 percent / DAST / CH2Cl2 / -78 deg C to r.t. 2: 95 percent / LiOH / acetonitrile; H2O / Ambient temperature 3: TFA / CH2Cl2 View Scheme