Which is better to start a reaction first amino group (nucleophilic site) or carboxylic group (electrophilic site)? Any suggestions will be appreciated.
With this type of zwitterionic compond, it depends on what you want to do, it is better to protect one end before going any further. Carboxylic acid group is not a very attractive electrophilic center. It is better to be detailed as to what you want to or may be the first step. I would suggest starting at the nucleophilic center if your reaction is to be done under milder conditions, However be prepared for a column/crystallization to remove a non-polar side product probably 20% or so.