g 1 11 moles was added over ten minutes with temperature not exceeding 80 u00b0 c after stirring for 15 minutes at 85 u00b0 c the mixture was cooled to 90 u00b0 c a solution of boc leucinaldehyde 159 g 0 738 moles in 400 ml thf was cooled to 70 u00b0 c and charged from a cooled addition funnel to the mixture over 15 minutes with temperature not exceeding 80 u00b0 c the mixture was stirred at 90 u00b0 c for 15 minutes with rapid stirring approximately 600 ml of 3n hcl was added allowing the temperature to rise to 5 u00b0 c over the course of the addition with the ph reaching 2 0 by litmus the mixture was then warmed to 10 u00b0 c and 2 liters of ethyl ether were charged to the mixture with vigorous agitation the phases were separated and the aqueous phase was again washed with 1 l ethyl ether the organic phases were combined washed with saturated nahco 3 400 ml and saturated nacl solution dried over mgso 4 filtered and stripped to an oil 211 1 g 94 yield boc statine ethyl ester 222 9 g 0 755 moles was charged to a 5 l flask containing 1 l dioxane giving solution 1 l h 2 o was added giving a cloudy suspension a ph meter was standardized at ph 10 using 50 50 dioxane ph 10 buffer the meter was used to monitor the addition of 50 naoh to the mixture over 45 minutes at a rate that maintained ph at 12 0 after ph had stabilized at 12 0 the mixture.