A method of making an amino acid triisocyanate is provided, the method comprising reacting an amino acid trihydrochloride with phosgene to form the amino acid triisocyanate. In some embodiments, the amino acid trihydrochloride comprises lysine ester trihydrochloride salt and the amino acid triisocyanate comprises lysine ester triisocyanate. In some embodiments, there is a lysine ester triisocyanate having a purity of at least about 98%, the lysine ester triisocyanate having a structure resulting from reacting lysine ester trihydrochloride salt with phosgene to form the lysine ester triisocyanate. These lysine ester triisocyanates can be used to make biodegradable polyurethanes.