Tritiated deltorphin analogues with high specific radioactivity and high affinity and selectivity for delta opioid receptors

Article abstract of DOI:10.1002/(SICI)1099-1344(199710)39:10<817::AID-JLCR28>3.0.CO;2-B

New conformationally constrained deltorphin I and II analogues were designed and synthesized, using a more lipophilic amino acid (Ile) instead of Val at positions 5 and 6, and 2-aminotetralin-2-carboxylic acid (Atc) at position 3. Two analogues (Tyr-D-Ala-(S)-Atc-Asp-Ile-Ile-Gly-NH₂ and Tyr-D-Ala-(R)-Atc-Glu-Ile-Ile-Gly-NH₂) with high potency and selectivity for δ opioid receptors were chosen for tritiation, with 3,5-I₂-Tyr¹-deltorphin analogues as precursors. Catalytic dehalotritiation of these precursors resulted in tritiated peptides with high specific radioactivity (1.28 TBq/mmol (34.5 Ci/mmol) and 1.33 TBq/mmol (36.0 Ci/mmol), respectively).