N‑Benzoyl-1,5-benzothiazepine and Its S‑Oxide as Vasopressin Receptor Ligands: Insight into the Active Stereochemistry around the Seven-Membered Ring

The stereochemistry of N-benzoyl-1,5-benzothiazepine and its S-oxide derivatives as vasopressin receptor ligands was examined in detail by freezing the conformation with a methyl group at the C6 or C9 of 1,5-benzothiazepine. It was revealed that the active forms recognized by the receptors are (cis,aS) for 1,5-benzothiazepine (5–7)-II and (cis,1S,aS) (syn) for its S-oxide (8–10)-II. The C9-methyl derivative of 1,5-benzothiazepine S-oxide (10-II) was designed and synthesized, achieving the putative active syn-isomer.