Sodium Bicarbonate → Boc-Pro-Pro-OH

Participants

Reaction Conditions

Reaction Steps

N-tert-butoxycarbonyl L-prolyl L-proline methyl ester 1 (1.10 g, 3.37 mmol) was dissolved in THF (23 mL) and the solution cooled to 0° C. (icebath). LiOH monohydrate (0.156 g, 3.72 mmol) was dissolved in de-ionized H2O (11.5 mL) and the solution cooled to 0° C. before being added dropwise to the solution of 1 over 5 min. The icebath was removed and stirring continued for an additional 3 h 30 min before solid NaHCO3 (0.566 g, 6.74 mmol) was added. Stirring was continued for 20 minutes and the THF evaporated. The solution was diluted with H2O (11.5 mL), washed with Et2O (2×11.5 mL) and acidified to pH 2 by addition of 2M aqueous H2SO4. The resulting solution was extracted with CH2Cl2 (70 mL+4×23 mL). The combined organic extracts were dried with anhydrous MgSO4 and the solvent evaporated affording the title compound as a white solid (0.933 g, 89%) with spectral characteristics in accordance with literature data1; δH(300 MHz; d6-DMSO) 12.41 (1H, br s, COOH), 4.45-4.21 (2H, m, CαH(Pro1)/CαH(Pro2)), 3.73-3.13 (4H, m, CδH2(Pro1)/CδH2(Pro2)), 2.29-1.61 (8H, m, CH2), 1.37/1.30/1.16 (9H, s, (CH3)3, all rotomers); δC (75 MHz; CDCl3) 173.8, 173.5, 173.3, 173.0, 154.6, 153.6, 79.9, 59.6, 59.5, 57.7, 57.6, 47.1, 47.0, 46.9, 46.7, 30.0, 29.2, 28.4, 28.3, 27.7, 27.5, 25.0, 24.2, 23.6; m/z (ESI) 335.1595 ([M+Na]+; C15H24N2O5Na requires 335.1582)

Provenance & Evidence