Efficient resolution of racemic crown-shaped cyclotriveratrylene derivatives and isolation and characterization of the intermediate saddle isomer

• Sven Götz,
• Andreas Schneider and
• Arne Lützen

Beilstein J. Org. Chem. 2019, 15, 1339–1346, doi:10.3762/bjoc.15.133

• substituents which reduces the symmetry from C3v to either C3 or C1 (Scheme 1) [14][15][16]. Ever since their first synthesis [17][18] these chiral CTV derivatives have gained much attention. This is especially true for their covalently assembled dimers, the so called cryptophanes pioneered by A. Collet as

• stable saddle conformers. A first example of such a saddle isomer of an achiral hexamethoxy-substituted CTV could be isolated and described by Luz and co-workers in 2004 [26]. At that time, they achieved this by heating the crown form to high temperatures and subsequent rapid cooling of the mixture

• . Isolation of the product was then possible through repeated column chromatography. Similarly, the same group was also able to isolate the saddle stereoisomer of a chiral nonamethoxy-substituted CTV in which every arene unit carries three additional substituents through HPLC on a chiral stationary phase [27

A hemicryptophane with a triple-stranded helical structure

• Augustin Long,
• Olivier Perraud,
• Erwann Jeanneau,
• Christophe Aronica,
• Jean-Pierre Dutasta and
• Alexandre Martinez

Beilstein J. Org. Chem. 2018, 14, 1885–1889, doi:10.3762/bjoc.14.162

• retained in solution. Keywords: CTV; hemicryptophanes; organic cages; triple helical structure; Introduction Among the remarkable architectures found in biological systems, those presenting a triple helical arrangement are of particular interest. Beside its classical double strand structure formed by

• in a propeller fashion. Other recent examples are the triple-stranded phenylene cages presenting a helical rod-like shape synthesized by Kirsche et al. [10]. Hemicryptophanes are chiral covalent cages combining a cyclotriveratrylene (CTV, north part) unit with another C3 symmetrical moiety (south

• have previously reported that the chirality unit in the south part and the chirality of the CTV unit in the north part influence each other, suggesting that the chirality of the CTV moiety could control the helical arrangement of the linkers [12][13]. We herein report the synthesis of the