Chiral Buckybowl Molecules

Abstract

Buckybowls are polynuclear aromatic hydrocarbons that have a curved aromatic surface and are considered fragments of buckminsterfullerenes. The curved aromatic surface led to the loss of planar symmetry of the normal aromatic plane and may cause unique inherent chirality, so-called bowl chirality, which it is possible to thermally racemize through a bowl-to-bowl inversion process. In this short review, we summarize the studies concerning the special field of bowl chirality, focusing on recent practical aspects of attaining diastereo/enantioenriched chiral buckybowls through asymmetric synthesis, chiral optical resolution, selective chiral metal complexation, and chiral assembly formation.

An Unrevealed Molecular Function of Corannulene Buckybowl Glycoconjugates in Selective Tumor Annihilation by Targeting the Cancer‐Specific Warburg Effect

“…As shown in Figure 3b , Cor‐gal exhibits a weak and multimodal CD spectrum in the UV range at room temperature due to the racemization of corannulene moiety through bowl‐to‐bowl inversion. [ 30 , 31 ] However, in the DNA complex, a significant increase of the negative Cotton effect curve of corannulene at 320 nm has been recorded indicating that an enantioenriched π ‐bowl isomer of Cor‐gal has formed during the DNA binding process. To determine the DNA‐binding parameters of the corannulene sugar‐conjugates, the thermodynamic profiles for Cor‐gal with hsDNA have been deciphered utilizing isothermal titration calorimetry (ITC) by a reverse titration method.…”

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

“…Among the PAHs, the buckybowls are of significant importance not only because of the presence of unique inherent chirality (bowl-chirality) originating either from the bowl structure itself, e.g., in hemifullerene or by the introduction of substituents (e.g., trimethylsumanene) or heteroatoms (e.g., triazasumanene) into the achiral bowls but also as they are partial structures of carbon nanotubes (CNTs) and fullerenes having bowl inversion activities as well as a tendency of crystal packing [ 17 – 20 ]. Since these chiral buckybowls contain stable convex or concave faces suitable for the generation of chiral molecular recognition sites which can be used for the construction of helical assemblies and have been used to coordinate the metal atom(s) [ 21 – 23 ]. On the other hands, further extension of these molecules leads to homochiral carbon nanotubes which can produce innovative perception in chiral sensing, chiral catalysis, separation techniques and chiral ligands for organocatalysis [ 24 ].…”

Synthesis of C70-fragment buckybowls bearing alkoxy substituents

“…Figure 2 shows the crystal structure of 5a. The crystal was obtained as a racemic compound containing a pair of two enantiomers defined by bowl chirality [26], as a result of the rapid bowl inversion under the crystallization conditions. 5a formed a columnar structure with alternative stack in convex-to-concave manner along the b axis with the overlap of the half part of the bowl structure ( Figure 2b).…”