Thank you Karthik

Even DMSO shall work as as a good solvent as we tend to dissolve many organic and metal complexes to check their cytotoxicity on animal cells.

From experience, it is usually not soluble but on addition of the base (DIPEA for example), which is responsible for the deprotonation o f the carboxyl functional group of the amino acid, renders the mixture into a homogeneous solution. You could also use NMP in place of DMF.