CALS News Fall 2011

Oxidation of 1,5-benzo­thiazepin-4-one (<b>5</b>-<b>A</b>) stereoselectively afforded the <i>S</i>-oxide <b>8I</b>-<b>A</b> (a<i>S</i>,1<i>S</i>) in preference to the diastereomer <b>8II</b>-<b>A</b> (a<i>S</i>,1<i>R</i>) affected by the remote stereogenic axis. All the enantiomers (<b>8I</b>-<b>A</b>/<b>8I</b>-<b>B</b> and <b>8II</b>-<b>A</b>/<b>8II</b>-<b>B</b>) were separated and isolated, and the interconversion between <b>8I</b> and <b>8II</b> (equilibrium ratio ≈5:1) was unequivocally verified to be caused by the rotation around the axis

Tolvaptan-Type Vasopressin Receptor Ligands: Important Role of Axial Chirality in the Active Form

The <i>anti</i> and <i>syn</i> isomers of tolvaptan-type compounds, <i>N</i>-benzoyl-5-hydroxy-1-benzazepines (<b>5a</b>–<b>c</b>), were prepared in a stereocontrolled manner by biasing the conformation with a methyl group at C9 and C6, respectively, and the enantiomeric forms were separated. Examination of the affinity at the human vasopressin receptors revealed that the axial chirality (a<i>S</i>) plays a more important role than the central chirality at C5 in receptor recognition, and the most preferable form was shown to be (<i>E</i>,a<i>S</i>,5<i>S</i>)

Tolvaptan-Type Vasopressin Receptor Ligands: Important Role of Axial Chirality in the Active Form

The <i>anti</i> and <i>syn</i> isomers of tolvaptan-type compounds, <i>N</i>-benzoyl-5-hydroxy-1-benzazepines (<b>5a</b>–<b>c</b>), were prepared in a stereocontrolled manner by biasing the conformation with a methyl group at C9 and C6, respectively, and the enantiomeric forms were separated. Examination of the affinity at the human vasopressin receptors revealed that the axial chirality (a<i>S</i>) plays a more important role than the central chirality at C5 in receptor recognition, and the most preferable form was shown to be (<i>E</i>,a<i>S</i>,5<i>S</i>)

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

The stereochemistry of <i>N</i>-benzoyl-1,5-benzothiazepine and its <i>S</i>-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 (<i>cis</i>,a<i>S</i>) for 1,5-benzothiazepine (<b>5</b>–<b>7</b>)-<b>II</b> and (<i>cis</i>,1<i>S,</i>a<i>S</i>) (<i>syn</i>) for its <i>S</i>-oxide (<b>8</b>–<b>10</b>)-<b>II</b>. The C9-methyl derivative of 1,5-benzothiazepine <i>S</i>-oxide (<b>10</b>-<b>II</b>) was designed and synthesized, achieving the putative active <i>syn</i>-isomer

<i>N</i>‑Benzoyl- and <i>N</i>‑Sulfonyl-1,5-benzodiazepines: Comparison of Their Atropisomeric and Conformational Properties

The atropisomeric and conformational properties of 1,5-benzodiazepines with an <i>N</i>-sulfonyl (<i>p</i>-tosyl/mesyl) group (<b>IIa</b>/<b>b</b>) were investigated by comparison with those of the <i>N</i>-benzoyl congeners (<b>I</b>). Similar to <b>I</b>, when the Ar–N­(SO₂) axis was frozen by a C9-substitution in the molecules, <b>IIa</b>/<b>b</b> were separated into the (a<i>R</i>)- and (a<i>S</i>)-atropisomers. The conformation of <b>IIa</b>/<b>b</b> revealed that the substituent (<i>p</i>-tolyl/methyl group) in the sulfonyl moiety occupies the position over the diazepine ring (folded form) in both the solid and solution states [e.g., (+)-(a<i>R</i>)-<i>N</i>-<i>p</i>-tosyl<b>-</b>1,5-benzodiazepin-2-one (<b>IIa-2</b>)], whereas that of <b>I</b> is <i>anti</i> to the diazepine ring [e.g., (−)-(a<i>R</i>)-<i>N</i>-benzoyl<b>-</b>1,5-benzodiazepin-2-one (<b>I-2</b>)], which was further supported by a computational study. The stereochemical stability also differed between the two congeners (e.g., Δ<i>G</i>^⧧: 104 kJ/mol for <b>I-2</b> and 132 kJ/mol for <b>IIa-2</b>)

Stereochemistry of <i>N</i>‑Benzoyl-5-substituted-1-benzazepines Revisited: Synthesis of the Conformationally Biased Derivatives and Revision of the Reported Structure

The <i>syn</i> (a<i>R</i>*,5<i>R*</i>) and <i>anti</i> (a<i>S</i>*,5<i>R*</i>) diastereomers of <i>N</i>-benzoyl-C5-substituted-1-benzazepines originating in the chiralities at C5 and the Ar–N­(CO) axis were first stereoselectively synthesized by biasing the conformation with a substituent at C6 and C9, respectively. Detailed examination of the stereochemistry (i.e., conformation and configuration) of these <i>N</i>-benzoyl-1-benzazepines by X-ray crystallographic analysis, VT NMR, and DFT calculations revealed new physicochemical aspects of these heterocycles including revision of the stereochemistry previously reported