Investigation of Beckett-Casy model 1: synthesis of novel 16,17-seco-naltrexone derivatives and their pharmacology.

Novel 16,17-seco-naltrexone derivatives 3 were synthesized using a 16-17 bond cleavage reaction of naltrexone as the key reaction to examine the Beckett-Casy model. All the prepared 16,17-seco-naltrexone derivatives 3 showed lower affinities for opioid receptors than naltrexone. Although the results of binding assay seem to support the existence of a cavity in the model, further investigation using 15,16-nornaltrexone derivatives 26 will be needed to confirm the model.