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With sodium hydroxide In tetrahydrofuran; water at 0 - 20℃; for 18 h;
A round bottomed flask containing methyl azetidine-3-carboxylate hydrochloride(3 g, 20 mmol), THF (30 mL) and H20 (30 mL) was added with an aqueous solution ofNaOH (4 M, 5 mL, 20 mmol) at 0 °C, followed by benzyl chloroformate (2.84 mL, 20 mmol). The reaction was vigorously stirred at room temperature for 18 hours. The reaction mixture was concentrated in vacuo and the residue partitioned between Et20 (100 mL) and H20 (30 mL). The aqueous phase was back-extracted withEt20 (3 x 50 mL), the combined organic phases were dried (Na2SO4) and concentrated in vacuo to give the title compound (5 g, 99percent) as a colourless oil, which was used in subsequent steps without further purification.‘H NMR (400 MHz, CDC13): ö 7.43-7.25 (m, 5 H), 5.10 (s, 2 H), 4.23-4.13 (m, 4 H), 3.74 (s, 3 H), 3.38 (q, J = 7.2 Hz, 1 H).
Stage #1: at 0℃; Stage #2: With acetic acid In methanol; hexanes; toluene
1-BENZYLOXYCARBONYL-3-AZETIDINECARBOXYLIC acid (from step (i); 9.3g, 39. 6MMOL) was dissolved in methanol (LOOML) and toluene (100mL), and cooled to 0°C. A solution of 2M trimethylsilyldiazomethane in hexanes was then added dropwise until bubbling had ceased and the yellow colour persisted. Acetic acid was then added dropwise until the yellow colour disappeared. Concentration of the solution yielded the title compound as an oil (9.48G, 38mmol, 96percent). IH NMR (400MHZ, CDC13) : 8 7.36-7. 31 (5H, m), 5.10 (2H, s), 4.19 (4H, D, J7. 8Hz), 3.75 (3H, s), 3.39 (1H, quintet, J 7. 8HZ).
EXAMPLE 27B; 1-benzyl 3-methylazetidine-1,3-dicarboxylate A solution of Example 27A (4.8 g, 20.3 mmol) in ether (100 ml) was treated with diazomethane (100 ml in ether, 60 mmol) at room temperature for 4 hours. Removal of the volatiles gave Example 27B (4.8 g Yield: 98percent). MS (DCI/NH3) m/z 250 (M+H)+.
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