p-Toluenesulfonic acid → HCID 14140251, compound

Participants

Reaction Steps

To a solution of N-carbobenzyloxy-L-alanine methyl ester (41.0 g, 0.71 mol) in 300 ml anhydrous toluene at -78° C., under N2, was added dropwise a toluene solution of diisobutyl-aluminum hydride (25% wt. % soln., 234 ml, 0.345 mol) over 0.5 hour. After the addition was complete the mixture was stirred 0.75 hour and quenched with the dropwise addition of 2N HCl (350 ml). The solution was warmed to room temperature and extracted with ethyl acetate. The combined organic layers were washed with brine and dried (MgSO4) and concentrated in vacuo. The residue was dissolved in 400 ml methanol and trimethylorthoformate (43 ml, 0.40 mol) and p-toluenesulfonic acid (0.723 g 3.8 mmol) was added. The mixture was stirred overnight and concentrated in vacuo to approximately 70% of the original volume. The residue was poured onto 800 ml of saturated NaHCO3. Ether and water were added. The aqueous layer was extracted with ether. The combined organic layers were washed with brine and dried (MgSO4) and concentrated in vacuo. Chromatography of the residue on HPLC using 30% ethyl acetate in hexanes as eluents provided the oily product N-carbobenzyloxy-L-alaninal dimethyl acetal.

Provenance & Evidence