S(Cl)(C)(=O)=O.[C:6]([O:10][C:11]([N:13]1[CH2:17][CH:16]([CH2:18]O)[CH:15]([OH:20])[CH2:14]1)=[O:12])([CH3:9])([CH3:8])[CH3:7].C(Cl)Cl.[N-:24]=[N+:25]=[N-:26].[Na+]>N1C=CC=CC=1>[C:6]([O:10][C:11]([N:13]1[CH2:14][CH:15]([OH:20])[CH:16]([CH2:18][N:24]=[N+:25]=[N-:26])[CH2:17]1)=[O:12])([CH3:9])([CH3:8])[CH3:7]Ms-Cl (0.38 mL, 2.6 eq) was added to a solution of 3-hydroxy-4-hydroxymethyl-pyrrolidine-1-carboxylic acid tert-butyl ester (mixture of stereoisomers, prepared according to WO9303026, 410 mg, 1.89 mmol) in pyridine (3.5 mL) at 0° C. The reaction mixture was stirred at 0° C. for 1 h. Then DCM was added and the mixture was washed with sat. aq. NaHCO3, dried over MgSO4, concentrated under reduced pressure and dried at HV. The crude mesylate was dissolved in DMF (18 mL), treated with NaN3 (1.23 g, 10 eq) and stirred at 95° C. for 1.5 h. After cooling to rt the mixture was concentrated to dryness and dissolved in DCM. The org. layer was washed with water, dried over MgSO4, concentrated under reduced pressure and the residue was purified by CC (DCM to DCM/MeOH 95:5) to afford the title intermediate as a yellow oil (390 mg, 85%).
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