Methanol → tert-butyl N-[(2S)-4-methyl-1-oxopentan-2-yl]carbamate

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Reaction Steps

Boc-L-Leucine methyl ester (22.7 g, 90 mmoles) in dry toluene (250 ml) under N2 was cooled to -78° and 25% di-isobutylaluminium hydride in toluene (130 ml, 225 mmoles) were added over 25 mins. keeping the temperature under -70°. The mixture was stirred for 15 mins. at -78° after completion of the addition, then MeOH (10 ml) was added cautiously. When effervescence ceased the mixture was poured into an ice-cold solution of Rochelle salt (100 ml of saturated solution +600 ml H2O). This mixture was shaken until an extractable solution was obtained. The toluene was separated and the aqueous phase re-extracted with ether (2×300 ml). Toluene and ether extracts were combined and dried (Na2SO4). The resulting oil was passed rapidly through a pad of silica gel in 15% EtOAc/petrol 40°-60°. The crude aldehyde was obtained as an oil, weight 18.68 g. Nmr showed aldehyde content to be b 85%, therefore yield of aldehyde: 15.9 g (83%).

Provenance & Evidence