Triethylamine → alpha-Azavalinyl-(L)-proline t-butyl ester

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Reaction Steps

Carbamoyl chloride 1 (4 mmol, crude), prepared as described above, was combined with carbazide 4 (3.50 mmol; 0.728 g) and triethylamine (0.557 ml; 4.00 mmol) in dry THF (2 ml). The mixture was heated at reflux for 7 hours, then filtered and evaporated to a thick oil. This was dissolved in benzene (10 ml) and hydrogenated with 10% Pd(C) (0.35 g) at 1 atm. for 6 hours. Filtration of the catalyst and evaporation gave a light yellow oil which was purified by flash chromatography on silica gel (CH2Cl2 --CH3OH, 50:1). There was obtained pure carbazide 5 (0.622 g; 2.30 mmol; 66%) as a light yellow solid. Recrystallization from hexanes gave a sample, mp 87°-91° C. TLC (silica gel; CH2Cl2 --CH3OH; 20:1) Rf=0.4. MS m/e 271 (M+). Analysis: Calculated for C13H25N 3 O3 : C, 57.54; H, 9.29; N, 15.48. Found: C, 57.67; H, 9.46; N, 15.44. NMR (CDCl3): δ1.08 (3H,d, J=6); 1.13 (3H, d, J=6); 1.43 (9H,s); 1.7-2.2 (4H,m); 2.4-2.7 (2H,m); 3.3 (2H,bs); 4.07 (1H, septet, J=6); 4.3-4.5 (1H,m). lR(CHCl3): 3600-3300, 1730, 1630 cm-1. [α]D =15.9°±b 0.5°. [α]d =15.9°±0.5°.

Provenance & Evidence