Hydrochloric Acid → (2R)-1-[(tert-butoxy)carbonyl]pyrrolidine-2-carboxylic acid

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Reaction Steps

Triethylamine (0.2 g, 2 mmoles) was slowly added to a solution of (D-proline (0.23 g, 2 mmoles) and t-BOC-ON (0.5 g, 2 mmoles) in DMF (3 mL) at room temperature and the mixture stirred for 36 h. The DMF was coevaporated with toluene under vacuum. Aqueous hydrochloric acid (1×10-4M) (20 mL) and ethyl acetate (20 mL) were added to the flask to dissolve the residue. The organic layer was washed with water (3×20 mL) and brine (2×20 mL); dried (5 g of MgSO4) and evaporated under reduced pressure. The residue, containing the product, was chromatographed on 5 g of silica gel column (1×25 cm). Upon evaporation under reduced pressure a transparent oil was obtained. The oil was crystallized from ethyl acetate/diethyl ether to give 0.4 g (2 mmoles) (99% yield) of a crystalline powder, mp 133°-134° C. (lit.91 mp 132°-133° C.). 1H-NMR (CDCl3) δ 1.46(9Ha,s); 1.86-2.40(4Hb,m); 3.43-3.80(2Hc,m); 4.26-4.66(1Hd,m); 11.43(1He,s). IR (Nujol) 1740, 1635 cm-1.

Provenance & Evidence