Isobutane → HCID 18391506, compound
Reaction equation
[CH2:1]([O:3][C:4](=[O:21])[C@@H:5]1[CH2:9][C@H:8]([OH:10])[CH2:7][N:6]1[C:11]([O:13][CH2:14][C:15]1[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=1)=[O:12])[CH3:2].CC(C)C>>[CH2:1]([O:3][C:4](=[O:21])[C@H:5]1[CH2:9][C@@H:8]([OH:10])[CH2:7][N:6]1[C:11]([O:13][CH2:14][C:15]1[CH:16]=[CH:17][CH:18]=[CH:19][CH:20]=1)=[O:12])[CH3:2]Participants
Procedure
N-CBZ-cis-4-hydroxy-D-proline (5.00 g, 18.8 mmol) was esterified by refluxing in ethanol (300 mL) containing a catalytic amount of p-toluenesulfonic acid monohydrate (0.3 g, 1.6 mmol). Wet ethanol was collected in a Dean-Stark trap. After 16 h, the trap was emptied whenever full until the reaction volume had decreased to about 50 mL. The tosic acid was neutralized with an excess of NaHCO3 (0.5 g, 6 mmol). After removal of volatiles in vacuo, the residue was diluted with ethyl acetate (100 mL) and the mixture stirred for 0.5 h to remove the oily product from the sodium salts. Solids were removed by filtration through Celite and the filter cake was washed with ethyl acetate (50 mL). Concentration of the combined filtrate and washings in vacuo provided 5.6 g (100%) of the crude cis hydroxy ester as a colorless oil: 1H NMR and IR spectra were identical in all respects to those of the enantiomer N-(benzyloxycarbonyl)-cis-4-hydroxy-L-proline ethyl ester; 13C NMR (75.5 MHz, CDCl3) δ 174.54, 174.35, 154.87, 154.21, 136.24, 136.11, 128.39, 128.31, 127.99, 127.96, 127.83, 127.74, 70.99, 70.01, 67.18, 61.88, 61.72, 58.17, 57.77, 55.90, 55.60, 38.54, 37.64, 13.93, 13.80; LRMS (CI, 70 eV, isobutane) m/e 294 (MH+, 81), 250 (100), 220 (23), 91 (66); HRMS (EI, 50 eV) m/e 293.1267 (293.1263 calcd for C15H19NO5).
Sources & evidence
- ORD record
- ord-eb209ca12a0d402f980ded2abf4c8030
- Source dataset
- uspto-grants-1999_08
- Patent number
- US05942537
Reaction notes
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