909406-73-1

909406-74-2

909406-73-1

General procedure for the synthesis of 6-oxaspiro[2.5]octane-1-carboxylic acid from ethyl 6-oxaspiro[2.5]octane-1-carboxylate: to a solvent mixture (THF:MeOH:H2O = 2:1:1, total volume 6 mL) containing ester B-6a (50 mg, 0.271 mmol) was added LiOH (65.0 mg, 2.71 mmol). The reaction mixture was stirred at 0 °C and subsequently brought to room temperature and continued stirring for 12 hours. Upon completion of the reaction, the mixture was cooled to 0 °C and the pH was adjusted with 1.5 N HCl solution to about 3. Next, the reaction mixture was extracted with DCM (2 x 50 mL), the organic phases were combined and washed with brine (25 mL), dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure to afford the target product Cap B-6 (35 mg) as a colorless liquid. The product was characterized by 1H NMR (CDCl3, δ=7.26 ppm, 300 MHz): δ3.83-3.68 (m, 4H), 1.85-1.81 (m, 2H), 1.62-1.42 (m, 3H), 1.21 (t, J=6.4 Hz, 1H), 1.07-1.01 (m, 1H).