87691-27-8

84348-37-8

87691-27-8

General procedure for the synthesis of N-Boc-cis-4-hydroxy-L-proline from (S)-1-(tert-butoxycarbonyl)-4-oxopyrrolidine-2-carboxylic acid: An appropriate amount of solvent was added to the reaction vessel and cooled to the specified temperature. Subsequently, the reducing agent (4.0~5.0 equivalents) was added in batches, taking care to control the rate of addition to avoid violent exotherm. The progress of the reaction was monitored by HPLC during the reaction. Upon completion of the reaction, the reaction solution was slowly poured into ice water to maintain the temperature at 0~5°C. The pH was adjusted to 0~5°C with dilute hydrochloric acid. The pH was adjusted to 2~3 with dilute hydrochloric acid and then extracted with ethyl acetate (EA) (5X each time, 3 times). All organic phases were combined, washed with saturated brine and dried with anhydrous sodium sulfate. The dried organic phase was concentrated under reduced pressure to give the crude product. Finally, the crude product was recrystallized in a mixed solvent of ethyl acetate and alkanes to give purified N-Boc-cis-4-hydroxy-L-proline.