TY  - JOUR
A1  - Weh, Manuel
A1  - Shoyama, Kazutaka
A1  - Würthner, Frank
T1  - Preferential molecular recognition of heterochiral guests within a cyclophane receptor
JF  - Nature Communications
N2  - The discrimination of enantiomers by natural receptors is a well-established phenomenon. In contrast the number of synthetic receptors with the capability for enantioselective molecular recognition of chiral substrates is scarce and for chiral cyclophanes indicative for a preferential binding of homochiral guests. Here we introduce a cyclophane composed of two homochiral core-twisted perylene bisimide (PBI) units connected by p-xylylene spacers and demonstrate its preference for the complexation of [5]helicene of opposite helicity compared to the PBI units of the host. The pronounced enantio-differentiation of this molecular receptor for heterochiral guests can be utilized for the enrichment of the P-PBI-M-helicene-P-PBI epimeric bimolecular complex. Our experimental results are supported by DFT calculations, which reveal that the sterically demanding bay substituents attached to the PBI chromophores disturb the helical shape match of the perylene core and homochiral substrates and thereby enforce the formation of syndiotactic host-guest complex structures. Hence, the most efficient substrate binding is observed for those aromatic guests, e. g. perylene, [4]helicene, phenanthrene and biphenyl, that can easily adapt in non-planar axially chiral conformations due to their inherent conformational flexibility. In all cases the induced chirality for the guest is opposed to those of the embedding PBI units, leading to heterochiral host-guest structures.
KW  - coordination chemistry
KW  - molecular capsules
KW  - stereochemistry
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-357750
VL  - 14
ER  - 
TY  - JOUR
A1  - Tshitenge, Dieudonné Tshitenge
A1  - Feineis, Doris
A1  - Mudogo, Virima
A1  - Kaiser, Marcel
A1  - Brun, Reto
A1  - Bringmann, Gerhard
T1  - Antiplasmodial Ealapasamines A-C,'Mixed' Naphthylisoquinoline Dimers from the Central African Liana Ancistrocladus ealaensis
JF  - Scientific Reports
N2  - Three unusual heterodimeric naphthylisoquinoline alkaloids, named ealapasamines A-C (1–3), were isolated from the leaves of the tropical plant Ancistrocladus ealaensis J. Léonard. These ‘mixed’, constitutionally unsymmetric dimers are the first stereochemically fully assigned cross-coupling products of a 5,8′- and a 7,8′-coupled naphthylisoquinoline linked via C-6′ in both naphthalene portions. So far, only two other West and Central Ancistrocladus species were known to produce dimers with a central 6,6″-axis, yet, in contrast to the ealapasamines, usually consisting of two 5,8′-coupled monomers, like e.g., in michellamine B. The new dimers 1–3 contain six elements of chirality, four stereogenic centers and the two outer axes, while the central biaryl axis is configurationally unstable. The elucidation of the complete stereostructures of the ealapasamines was achieved by the interplay of spectroscopic methods including HRESIMS, 1D and 2D NMR (in particular ROESY measurements), in combination with chemical (oxidative degradation) and chiroptical (electronic circular dichroism) investigations. The ealapasamines A-C display high antiplasmodial activities with excellent half-maximum inhibition concentration values in the low nanomolar range.
KW  - structure elucidation
KW  - stereochemistry
KW  - Ancistrocladus ealaensis
KW  - dimers
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170645
VL  - 7
IS  - 5767
ER  -