i was asked to synthesis this compound from this amino acid, i first alkylated the alpha carbon using enolate alkylating method then i esterficated the amino acid but i'm doubtful that my steps are right, do i need to protect the amino group in the esterification step? or even before ?
I think you need a protection strategy and there are several choices. This one uses O'Donnell's benzophenone imine strategy details here.
First you prepare glycine ethyl ester hydrochloride from glycine with EtOH/HCl, a method is here patent.
From the ethyl ester hydrochloride prepare the benzophenone imine by O'Donnell's method as described in ref 1. This gives a protected species that can be easily alkylated under phase-transfer conditions with allyl bromide as described in ref 1
The allyl product is then epoxidised (MCPBA) and the epoxide opened with iodide procedure here
Deprotection with acid hydrolysis gives your target molecule.