Using Lithium Hydroxide at small excesses can often safely de-esterify an amino acid ester. There is always a possibility of racemization, so best to do it carefully, and not heat it. You can sometimes add a little H2O2 to help speed it up if it is too slow, even an old bottle of THF with trace peroxides can sometimes make it work better. Best is to use 1-2 M LiOH in water and go 50:50 in THF. Sometimes, you even need to add a trace of methanol for solubility, which will slow it down some, but not hurt much.