.beta.-Casomorphin-4-NH2 74135-04-9 AIDS-002088 AIDS002088 H-Tyr-Pro-Phe-Pro-NH2 L-Prolinamide, L-tyrosyl-L-prolyl-L-phenylalanyl- Morphiceptin Tyr-Pro-Phe-Pro-NH2 b-Casomorphin-4-amide