(N-methylpyridinium)insulins. Modification at the A19- and B16-tyrosines.

Reaction of 2-iodo-N-methylpyridinium iodide with insulin gave, amongst others, A19- and B16-(N-methylpyridinium)insulin derivatives in which the phenolic groups of the respective tyrosines had been modified. Under carefully controlled conditions the A19 derivative gave small rhombohedral crystals, whereas the B16 derivative failed to crystallize. Both these derivatives had low biological activities.