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Aqueous sodium hydroxide (1N, 32.4 mL, 32.4 mmol) was added to a scalemic mixture enriched in (1S,2R,4R)-ethyl 2-ethyl-4-hydroxycyclopentanecarboxylate (3.02 g, 16.21 mmol) and the reaction mixture was stirred at ambient temperature overnight. Ether (15 mL) was added and the layers were separated. The aqueous layer was cooled to about 0° C. Aqueous HCl (5N) was slowly added to bring pH to about 1. The aqueous suspension was extracted with EtOAc (4×40 mL). The combined organic layers were washed with brine (50 mL), dried over anhydrous MgSO4, filtered and concd under reduced pressure to give a scalemic mixture enriched in (1S,2R,4R)-2-ethyl-4-hydroxycyclopentanecarboxylic acid (2.56 g, 100%): LC/MS (Table 1, Method b) Rt=1.36 min; MS m/z: 157 (M−H)−.

1. customthe layers were separated
2. temperatureThe aqueous layer was cooled to about 0° C
3. additionAqueous HCl (5N) was slowly added
4. extractionThe aqueous suspension was extracted with EtOAc (4×40 mL)
5. washThe combined organic layers were washed with brine (50 mL)
6. dry with materialdried over anhydrous MgSO4
7. filtrationfiltered
8. customto give a scalemic mixture