128 56 139 97 170 47 to a biphasic solution of 0 40 g of threo ethylester hydrochloride salt in 2 ml of water and 10 ml of ether was added 0 43 g of sodium carbonate followed by 0 42 g of carbobenzyloxy chloride at 0 u00b0 c the reaction mixture was vigorously stirred at room temperature for 1 h then the organic layer was separated and the aqueous layer was twice extracted with 50 ml portions of dichloromethane the combined organic extract was concentrated to give 0 32 g of ethyl 2r 3s 2 hydroxy 3 benzyloxycarbonylamido 3 phenylpropionate as a colorless solid m p 107 108 u00b0 c u03b1 d 25 13 3 u00b0 meoh c 1 2 1 h nmr cdcl 3 u03b4 1 23 t 3h j 7 0 3 18 bs 1 4 22 q 2 j 7 0 4 42 bs 1 5 03 m 2 5 25 d 1 j 9 5 5 66 d 1 j 9 5 7 20 7 35 m 10 13 c nmr cdcl 3 u03b4 13 89 56 45 62 29 66 82 73 40 126 65 127 63 127 95 128 04 128 32 128 42 136 17 138 85 155 63 172 00 to a solution of 10 0 g of 2s 3s 2 hydroxy 3 amino 3 phenylpropionamide in 100 ml of methanol was slowly added 16 ml of acetyl chloride at 0 u00b0 c the reaction mixture was.