Trifluoromethanesulfonic acid → (1S,2R,3R,5R,6S)-2-azido-3-benzyloxybicyclo[3.1.0]hexane-2,6-dicarboxylic acid 2-benzyl ester 6-ethyl ester

Participants

Reaction Steps

To a solution of (1S,2R,3R,5R,6S)-2-azido-3-hydroxy-bicyclo [3.1.0]hexane-2,6-dicarboxylic acid 2-benzyl ester 6-ethyl ester (VII) (305 mg, 0.88 mmol) and benzyl 2,2,2-trichloroacetimidate (0.2 mL, 1.06 mmol) in cyclohexane (2.4 mL) and DCM (1.2 mL) was added TfOH (0.05 mL), whereupon the solution became hot and stirring was continued at 23° C. for 5 h. The reaction mixture was poured on ice, diluted with ether, washed with sat. NaHCO3 -sol., brine and dried over MgSO4. The crude product was purified by silica gel column chromatography with hexane/EtOAc 4:1 to give (1S,2R,3R,5R,6S)-2-azido-3-benzyloxybicyclo[3.1.0]hexane-2,6-dicarboxylic acid 2-benzyl ester 6-ethyl ester (XXIII-3) (102 mg, 27%) as a yellow oil. 1H-NMR (250 MHz, CDCl3) □1.25 (3H, t, J=7.1 Hz), 1.75 (1H, t, J=3.5 Hz), 2.06 (1H, m), 2.17-2.31 (3H, m), 3.60 (1H, bt, J=8 Hz), 4.12 (2H, q, j=7.1 Hz), 4.42 (1H, d, J=12 Hz), 4.57 (1H, d,J=12 Hz), 5.23 (1H, d,J=12 Hz), 5.34 (1H, d,J=12 Hz), 7.15-7.42 (10H, m); MS[ISP] 408 [(M+H-N2)+ ]; □D20 +2.03 ° (c=0.99, CHCl3).

Provenance & Evidence