First synthesis and characterization for the stereoisomers of Ulipristal acetate

• We have succeeded in synthesizing the stereoisomers of Ulipristal acetate.
• The structure of each stereoisomer was confirmed for the first time.
• The structure of the key intermediate 5 was confirmed by single-crystal X-ray analysis.
• About 0.2% of 11α,17α-isomer I was presented in the Ulipristal acetate synthesized by Dancsi’s route.
• There was about 0.14% of 11β,17β-isomer III in the Ulipristal acetate synthesized by our route.

The three stereoisomers, 11α,17α-isomer I, 11α,17β-isomer II and 11β,17β-isomer III are related substances of the selective progesterone receptor modulator Ulipristal acetate. Herein, we presented an efficient and practical synthesis approach to deliver these three stereoisomers for the first time, and also confirmed the structure of the key intermediate 5a by single-crystal X-ray analysis. Our research will be of immense help for organic chemists to study the impurity profile of Ulipristal acetate.

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