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The requisite epoxide 211 for the enantioselective ring-opening reaction was prepared according to the method of Noyori (Suzuki, M.; Oda Y., Noyori, R. J. Am. Chem. Soc. 1979, 101, 1623-1625). Thus, 3-cyclopentenone was synthesized via the Pd(0)-catalyzed rearrangement of 3,4-epoxycyclopentene, a reaction remarkable both for the efficiency of catalysis and the ease of the experimental procedure. Epoxidation of 3-cyclopantenone was effected with trifluoroperacetic acid to afford 3,4-epoxycyclopentanone (211) in 60% isolated yield after distillation. We found that treatment of the trifluroacetic anhydride with hydrogen peroxide urea addition compound provided a useful alternative to the literature method for the preparation of trifluoroperacetic acid Noyori's procedure for preparation of trifluoroperacetic acid specifies the use of 90% H2O2. Overall, this two-step sequence provided multigram quantities of epoxide 211 in pure form with no chromatographic purification necessary.

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