Total synthesis of (±)-heliannuol C and E via aromatic Claisen rearrangement

Total Synthesis of (–)‐Heliespirone A and (+)‐Heliespirone C

“…[15] We therefore attempted a Brønsted-acid-catalysed rearrangement with benzoic acid (pK a = 4.2; Table 1, Entry 4). [17] With compound 14 in hand, our attention turned to the kinetic resolution using a Sharpless AD reaction (Scheme 3). Using a stronger carboxylic acid, trifluoroacetic acid (pK a = 0.23; Table 1, Entry 5), did not lead to rearrangement, but it did allow the trisubstituted alkene to participate in a hydration reaction upon aqueous workup to give undesired compound 19.…”

Synthesis of substituted Z-styrenes by Hiyama-type coupling of oxasilacycloalkenes: application to the synthesis of a 1-benzoxocane

“…The various approaches to the heliannuols have recently been reviewed [ 34 ]. We have previously reported syntheses of heliannuols C, D, and E via intramolecular epoxide opening reactions [ 35 – 36 ], but this approach did not translate well to the synthesis of heliannuol A. One of our alternative strategies for the synthesis of heliannuol A was an intramolecular Buchwald–Hartwig etherification of a Z -styrene derivative to provide a conformational constraint to facilitate the formation of the eight-membered ring [ 37 ].…”

Synthesis of Diverse Oxa‐Carbocycle‐Annulated Flavones Using the Combined Claisen Rearrangement and Ring‐Closing Metathesis

“…The structural features and wide range of biological activity attracted organic chemists for the synthesis of these heterocycles fused to other bioactive heterocycles. Some of the pharmacologically important heterocyclic ring‐fused flavones (cyclomorusin and artoflavone A) and oxepine ring containing biologically active natural products (ptaeroxylin, heliannuols A) are shown in Fig . .…”