Methanol → tert-butyl N-[(2S)-1-oxo-3-phenylpropan-2-yl]carbamate

Participants

Reaction Conditions

Reaction Steps

N-t-Butoxycarbonyl-L-phenylalanine methyl ester (250 g., 0.90 mol) was dried by addition and removal at reduced pressure of 1.0 l dry toluene, and dissolved in dry toluene (3 l.) in a 12 l flask equipped with septum, nitrogen inlet, overhead stirrer, and thermometer. The solution was cooled to -78° C. and a solution of diisobutylaluminum hydride was added via cannula over a period of 0.5 hour so that the temperature was maintained below -70° C. After being stirred an additional 15 minutes, absolute methanol (250 ml.) was added (dropwise at first until vigorous effervescence subsided) at -78° C. followed 20 minutes later by 3.0 l of 50% Rochelle salt solution (also slowly at first). Diethyl ether (2 l) was added to the mixture, and the temperature was raised to 20° C. On standing the layers separated, and the aqueous was extracted with ether (2×1.5 l). The organic phase was washed with brine, dried sodium sulfate and concentrated to give crude N-t-butoxycarbonyl-L-phenylalaninal which was used immediately without purification.

Provenance & Evidence