7 mmol was dissolved in toluene 90 ml 4 bromobenzyl bromide 17 5 g 70 1 mmol was added and the reaction was cooled to about u2014 10 u00b0 c potassium tert butoxide 8 6 g 76 5 mmol was added at such a rate that the temperature did not exceed 0 u00b0 c the reaction stirred in the cold bath for two hours then was diluted with ether and washed with water 150 ml the organic layer was dried sodium sulfate filtered and concentrated in vacuo to afford a clear yellow oil this was treated with 1n hcl 100 ml 100 mmol and stirred overnight the reaction was extracted with ethyl acetate 100 ml and the aqueous layer was to afford 14 1 g of the racemic amino ester hydrochloride 68 7 yield isocyanate derivatives can be made by reacting the aminoacid ester with a phosgene equivalent such as trichloromethyl chloroformate this is exemplified in the synthetic examples below the racemic compounds can be resolved into their component enantiomers via a number of known techniques ethyl 2 r amino 2 4 bromobenzyl propanoate was produced from racemic ethyl 2 amino 2 4 bromobenzyl propanoate by the following procedure to 1 3 l of a buffer made from 13 69 g kh 2 po 4 and 2 l of water was added 20 g of the commercially available enzyme.