2-Alanyl-5-norleucine-enkephalin sulfonic acid 75829-10-6 Enkephalin sulfonic acid, ala(2)-nle(5)- Enkephalin sulfonic acid, alanyl(2)-norleucine(5)- Esa, A(2)-N(5)- L-Phenylalaninamide, L-tyrosyl-D-alanylglycyl-N-(1-sulfopentyl)-, (R)-