A crystalline A14-(2-nitro-4-trimethylammoniophenyl) derivative of bovine insulin.

[O-(2-Nitro-4-trimethylammoniophenyl)-TyrA 14]insulin (bovine) is a product formed on reaction of bovine insulin with the hydrophilic reagent 1-fluoro-2-nitro-4-trimethyl-ammoniobenzene iodide (TAN-F) in an aqueous buffer at pH 8.00. The derivative was isolated and its purity established by standard procedures. The identity of the derivative was determined by degrative studies with alpha-chymotrypsin. The addition of zinc to the above reaction decreases the yield of the title derivative, but increases the yield of the [N alpha-TAN-GlyA1] derivative. [N alpha-Boc-GlyA1]insulin was also reacted with the above mentioned reagent in an attempt to improve the yield of the A14-tyrosine derivative. The biological activity of this microcrystalline derivative was found to be 12.4 units/mg as measured by the mouse convulsion assay.