Determination of the absolute configuration of (+)- and (-)-N-CBZ-3-fiuoropyrrolidine-3-methanol using vibrational circular dichroism and confirmation of stereochemistry by conversion to (R)-tert-butyl 3-fluoro-3-(((R)-1-phenylethyl)carbamoyl)pyrrolidine-1-carboxylate

Racemic N-CBZ-3-fluoropyrrolidine-3-methanol (+/-)-1 was resolved by preparative chiral HPLC. The absolute configuration of the enantiomers of 1 was identified by vibrational circular dichroism and confirmed by chemical synthesis, which involved exchanging the CBZ protecting group of (-)-1 with Boc, followed by oxidation with RuCl3, NaIO4, activation of the resulting acid with carbonyl diimidazole and reaction with (R)-alpha-methylbenzylamine to give (R)-tert-butyl 3-fiuoro-3-(((R)-1-phenylethyl)carbamoyl) pyrrolidine-l-carboxylate 7. The latter was compared with authentic (S)-tert-butyl 3-fluoro-3-(((R)-1phenylethyl)carbamoyl)pyrrolidine-l-carboxylate 6 and its diastereomer 7; the configuration of diastereomer 6 was obtained by an X-ray diffraction study. This established that the enantiomer (-)-1 had an (R)-configuration. (C) 2016 Elsevier Ltd. All rights reserved.