Sulfuric Acid → Ethyl (1R,2S)-1-amino-2-ethenylcyclopropanecarboxylate sulphate (2:1)

Participants

Reaction Conditions

Reaction Steps

An ethyl acetate solution of the (1R,2S)-1-amino-1-ethoxycarbonyl-2-vinylcyclopropane obtained in Example 30 was cooled to 2° C., and then, using a dropping funnel, 69.34 g (1.372 mmol) of 97% sulfuric acid was added dropwise thereto over 50 minutes. Sulfuric acid remaining in the dropping funnel was transferred to the mixture using 87.64 g of ethyl acetate. Thereafter, the temperature of the mixture was increased to 40° C., and the mixture was then concentrated under reduced pressure to result in a liquid amount of 3.2 L. To the obtained concentrate, 1.2606 kg of toluene was added, and the mixture was then cooled to 0° C. over 2 hours. After the mixture had been kept cold at 0° C. for 2 hours, the generated crystal was collected by filtration. The obtained crystal was washed with 420.3 g of toluene, and it was then dried at room temperature for 2 hours under nitrogen current. Thereafter, it was dried under reduced pressure at 40° C. for 10 hours, so as to obtain 267.79 g of (1R,2S)-1-amino-1-ethoxycarbonyl-2-vinylcyclopropane hemisulfate salt in the form of a white crystal.

Provenance & Evidence