Hydrochloric Acid → Ethyl trans-4-hydroxy-L-prolinate hydrochloride

Participants

Reaction Steps

Trans-4-hydroxy-L-proline was treated with EtOH and HCl gas, and the mixture was evaporated to give trans-4-hydroxy-L-proline ethyl ester hydrochloride. This product was treated with TsCI and Et3N in CH2Cl2, to give after aqueous workup N-(toluene-4-sulfonyl)-trans-4-hydroxy-L-proline ethyl ester. This product was treated with morpholinosulfur trifluoride in CH2Cl2, to give after aqueous workup N-(toluene-4-sulfonyl)-cis-4-fluoro-L-proline ethyl ester. This product was treated with NaOH in CH3OH and H2O to give, after acidification, extraction, drying with MgSO4, filtration and evaporation, N-(toluene-4-sulfonyl)-cis-4-fluoro-L-proline. This product was treated with HCl.Phe-OBn, BOP, and NMM in DMF, to give after aqueous workup and flash chromatography the title compound as a clear oil.

Provenance & Evidence