2,2,2-Trifluoroethanol → benzyl (1S,3S,4S)-3-acetamido-4-allyl-3-(tert-butylcarbamoyl)cyclopentylcarbamate

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A stirred mixture of benzyl 3-allyl-4-oxocyclopentylcarbamate, mixture of isomers (5.19 g, 19 mmol) and ammonium acetate (5.86 g, 76 mmol) in 2,2,2-trifluoroethanol (20 mL) under nitrogen was treated with t-butylisonitrile (6.50 mL, 57 mmol) and stirred at room temperature for 3 days. The reaction mixture was concentrated in vacuo, dissolved in dichloromethane and added to a silica gel column (˜550 cc). Successive elution with 60%, 70%, and 80% ethyl acetate/heptane afforded the subject compound together with an undesired isomer (total 3.48 g). Recrystallization (2 crops) from minimum acetonitrile/ether gave the subject compound (1.83 g, 23%) as a white solid. NMR (CDCl3): δ 7.38 (br s, 5 H), 7.10 (br s, 1 H), 5.65-5.80 (m, 1 H), 5.67 (br s, 1 H), 4.95-5.15 (m, 4 H), 4.25-4.35 (m, 1 H), 2.85-3.00 (m, 1 H), 2.60-2.70 (m, 1 H), 2.20-2.35 (m, 2 H), 1.85-2.15 (m, 3 H), 2.03 (s, 3 H), 1.40 (s, 9 H). MS (M+1): 416.1.

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