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温度

0 °C

Triethylamine (29.0 mL, 208 mmol) was added to a solution of 1,4-dioxa-8-aza-spiro[4.5]-decane-6-carboxylic acid methyl ester (91) (16.6, 82.5 mmol) in CH2Cl2 (159 mL, 0.5 M). The solution was cooled to 0° C. in an ice bath, then benzoylchloroformate (12.8 mL, 89.9 mmol) was added dropwise, with stirring, over 40 minutes. When the reaction was judged complete by TLC (0.75 h), the solution was concentrated in vacuo and purified by silica gel chromatography (10:3 Hexanes:EtOAc) to provide pure 8-benzyloxycarbonyl-1,4-dioxa-8-aza-spiro[4.5]-decane-6-carboxylic acid methyl ester (92) (23.43 g, 85%). 1H NMR (CDCl3): 7.41–7.25 (5H, m), 5.10 (2H, broad s), 4.02–3.50 (11 H, m), 2.80–2.62 (1H, broad s), 2.20–2.00 (1H, broad s), 1.70–1.50 (1H, broad s) ppm. 13 C NMR (CDCl3): 170.26, 154.88, 136.47, 128.32, 127.86, 127.74, 106.78, 67.09, 64.90, 64.59, 51.71, 48.63, 43.94, 41.76, 33.15 ppm.

1. customwas judged complete by TLC (0.75 h)
2. concentrationthe solution was concentrated in vacuo
3. custompurified by silica gel chromatography (10:3 Hexanes:EtOAc)