(R)-tert-butyl 3-aminopyrrolidine-1-carboxylate hydrochloride

Synthesis

Step 10-3: Preparation of (R)-1-(tert-butoxycarbonyl)-3-aminopyrrolidine hydrochloride: according to the method described in Step 10-1, 2.60 g of (R)-1-(tert-butoxycarbonyl)-3-aminopyrrolidine (chemical purity: 48.7 area %, optical purity: 96.6% ee, relative to the (R)-3-aminopyrrolidine-1-carboxylic acid tert-butyl ester hydrochloride HPLC area value, containing 48.4% optically active 1-(tert-butoxycarbonyl)-3-methoxypyrrolidine (represented by formula (9)) and 31.9% 1-(tert-butoxycarbonyl)-3,4-dehydropyrrolidine (represented by formula (10)) was dissolved in 30 mL of isopropanol. To this solution was added 1.39 g of concentrated hydrochloric acid followed by concentration under reduced pressure. To the concentrate was added 50 mL of ethyl acetate and stirred at 22°C for 30 minutes. After continued stirring for 30 minutes under ice bath cooling, the crystals were collected by filtration under reduced pressure. The crystals were washed with 20 mL of ethyl acetate and subsequently dried under vacuum to afford 2.51 g of white solid (R)-tert-butyl (R)-3-aminopyrrolidine-1-carboxylate hydrochloride (chemical purity: 99.6 area %, yield: 95%, optical purity: 99.7% ee). It was confirmed by HPLC analysis that optically active 1-(tert-butoxycarbonyl)-3-methoxypyrrolidine represented by formula (9) and 1-(tert-butoxycarbonyl)-3,4-dehydropyrrolidine represented by formula (10) were not detected.

References

[1] Patent: EP2050735, 2009, A1. Location in patent: Page/Page column 22