[LG05]

Could someone suggest any compound which reacts with amine in water and forms acid functionalities besides cyclic anhydride or bromo/chloro alkyl acid?

Homogenous reactions are preferred.

Thanks.

[HP]

I suggest reaction of your amine with succinic anhydride but the water will act to hydrolize some part of the anhydride to succinic acid...If you are using carboxylic acids its possible to couple them to the amine in aqueous media using water-soluble carbodiimide like EDC as coupling agent.
Success!