Sie können Bookmarks mittels Listen verwalten, loggen Sie sich dafür bitte in Ihr SLUB Benutzerkonto ein.
Medientyp:
E-Artikel
Titel:
Internal Nucleophilic Termination in Acid‐Mediated Polyene Cyclisations: Synthetic access to methyle homologs of (±)‐Ambrox® and its diastereoisomers
Beteiligte:
Snowden, Roger L.;
Eichenberger, Jean‐Claude;
Giersch, Wolfgang;
Thommen, Walter;
Schulte‐Elte, Karl H.
Beschreibung:
<jats:title>Abstract</jats:title><jats:p>Treatment of ten monocyclic dienols <jats:bold>8–11</jats:bold> with an excess of fluorosulfonic acid in 2‐nitropropane at −90° afforded diastereoisomeric mixtures of racemic tricyclic ethers <jats:bold>12–14</jats:bold> in 81–91% yield (see <jats:italic>tables 1 and 2</jats:italic>). These transformations represent further examples of biomimetic acid‐mediated cyclisations in which an OH group serves as the internal nucleophilic terminator. A non‐synchronous process is postulated, and the examples described strongly re‐inforce our working mechanistic hypothesis, whereby the stereochemical course of cyclisation is directed by the orientation of the side chain vicinal to the intermediate cyclohexyl cation (<jats:italic>see Schemes 4 and 5</jats:italic>). It is also demonstrated that the efficiency of this process is independent of the nature of the OH group, which may be primary, secondary, or tertiary. In addition, the organoleptic properties of <jats:bold>12–14</jats:bold>, Me homologs of known odorants such as <jats:italic>Ambrox®</jats:italic> ((−)‐<jats:bold>3a</jats:bold>) and its diastereoisomer, are briefly discussed.</jats:p>