Intrinsic chirality of triple‐layered naphthalenophane and related graphs

We prove that the graph of triplelayered naphthalenophane and an infinite class of related graphs are all intrinsically chiral. We also give examples to illustrate that not all graphs which are contractible to a Möbius ladder with three rungs are necessarily intrinsically chiral.     

One-pot Crabbé homologation-radical cascade cyclisation with memory of chirality

The tandem Crabbé homologation-radical rearrangement of terminal enediynes leads, in a one-pot procedure, to the enantioselective synthesis of six- and seven-membered ring α-aminoesters bearing a quaternary stereocenter based on the phenomenon of memory of chirality.     

Synthesis of P,N-2,2′-biphenyl derivatives with central chirality

Enantiopure 2-(dicyclohexylphosphino)-1,1′-biphenyl derivatives substituted in the 2′-position by a chiral amino group were prepared. For the compound bearing an acyclic chiral chain, the key step was a Suzuki coupling between bromobenzeneboronic acid and N-Boc-iodoaniline whereas an aromatic nucleophilic substitution allowed the introduction of a chiral pyrrolidine in the 2′-position of the biphenyl backbone. The efficiency of the P,N-biphenyl pyrrolidine derivatives as ligands in Pd-catalyzed arylaminations compares well with that of DavePhos ligand.     

Construction of molecular nanotubes with precise length,diameter and chirality

<正>Molecular nanotubes are nanoscale organic materials with tubular architecture, that show potential applications in molecular recognition/separation, cross-membrane transportation, catalysis in confined spaces, and nanoelectronics [1]. However, the precise construction of molecular nanotubes with well-defined cavity sizes and shapes is non-trivial.     

Axial chirality of N,N′-disubstituted 3,4-ethylenedioxythiophene-2,5-dicarboxamides

A series of N,N’-disubstituted 3,4-ethylenedioxythiophene-2,5-dicarboxamides was synthesised by amide bond formation between 3,4-ethylenedioxythiophene-2,5-dicarbonyl chloride and corresponding primary amines, where the size and the nature of the substituent were varied. The crystal structures of prepared compounds were determined by X-ray structure analysis. Mechanism and reaction rates of interconversion between conformational isomers were obtained by DFT calculations. All studied compounds reveal axial chirality with molecular symmetry C ₂. Amide bond isomerisation and twisting of the dioxane ring in studied compounds results in the formation of series of conformers of which the s-trans/s-trans conformer is energetically most favourable.     

Measuring the optical chirality of molecular aggregates at liquid–liquid interfaces

Some new experimental methods for measuring the optical chirality of molecular aggregates formed at liquid–liquid interfaces have been reviewed. Chirality measurements of interfacial aggregates are highly important not only in analytical spectroscopy but also in biochemistry and surface nanochemistry. Among these methods, a centrifugal liquid membrane method was shown to be a highly versatile method for measuring the optical chirality of the liquid–liquid interface when used in combination with a commercially available circular dichroism (CD) spectropolarimeter, provided that the interfacial aggregate exhibited a large molar absorptivity. Therefore, porphyrin and phthalocyanine were used as chromophoric probes of the chirality of itself or guest molecules at the interface. A microscopic CD method was also demonstrated for the measurement of a small region of a film or a sheet sample. In addition, second-harmonic generation and Raman scattering methods were reviewed as promising methods for detecting interfacial optical molecules and measuring bond distortions of chiral molecules, respectively.     

1,1'-Binaphthol annulated perylene diimides: Aggregation-induced emission enhancement and chirality inversion

Aggregation-induced emission enhancement and aggregation-induced chirality inversion are two individual phenomena for the enantiomerically pure organic dyes in the aggregates. Herein we reported for the first time that these two interesting phenomena could be observed simultaneously in the aggregated states of enantiomerically pure S/R-1,1’-binaphthol annulated perylene diimides, in which two perylene diimides moieties were bridged by S/R-1,1’-binaphthol(BINOL) at the bay positions. Owing to the...     

Remarkable difference of phospholipid molecular chirality in regulating PrP aggregation and cell responses

Prion diseases are fatal neurodegenerative diseases that can cause severe dementia.The misfolding and accumulation of the prion peptide (Pr P)_106–126is crucial,and this process is closely relevant to biological membranes.However,how Pr P_106–126aggregation is affected by the molecular chirality of phospholipid membrane is unknown.Thus,in this study,a pair of L-and D-aspartic acid (Asp)-modified 1,2-dipalmitoyl-sn–glycero-3-phosphoethanolamine (DPPE) were synthesized to const...     

Synthesis of new deazaflavins with planar chirality. Redox-induced “rope-skipping” racemization

New 5-deazaflavins with planar chirality (dFl(n)) were synthesized in which N(3) and O(2′α) in the 10-(2′-hydroxy)phenyl group were linked by a

chain (n=8,10). (+)-dFl(n=8) showed a large chiral discrimination in fluorescence quenching by (R)- and (S)-1,1′-bi-2- naphthol. (+)-dFl(n=10), which was optically stable at ambient conditions, racemized only when it was converted to the reduced form. This is the first example for redox-induced rope-skipping racemization.     

Simultaneous enhancement of phosphorescence and chirality by host–guest recognition of molecular tweezers

A novel type of host–guest recognition systems have been developed on the basis of a Au(III) molecular tweezer receptor and chiral Pt(II) guests. The complementary host–guest motifs display high non-covalent binding affinity (K_a: ～10⁴ L/mol) due to the participation of two-fold intermolecular π–π stacking interactions. Both phosphorescence and chirality signals of the Pt(II) guests strengthen in the resulting host–guest complexes, because of the cooperative rigidifying and shielding effects rendered by the tweezer receptor. Their intensities can be reversibly switched toward pH changes, by taking advantage of the electronic repulsion effect between the protonated form of tweezer receptor and the positive-charged guests in acidic environments. Overall, the current study demonstrates the feasibility to enhance and modulate phosphorescence and chirality signals simultaneously via molecular tweezer-based host–guest recognition.     

Molecular chirality induction to an achiral π-conjugated polymer by circularly polarized light

A preferred-handed helical conformation was induced to poly(9,9-dioctylfluoren-2,7-diyl) (PDOF) in a thin film form upon irradiation with single-handed circularly polarized light (CPL) where the induction was reversible.     

“Geländer” macrocycles: Synthesis,chirality and racemisation barriers

A new class of axially-chiral o,o′-bridged biphenyls containing etheroxime chains was obtained in good yields by the macrocyclisation reaction of o,o′-diformylbiphenyl dioxime with several ditosylated or dibrominated reagents. In all cases the enantiomers of the compounds were separated by HPLC using a chiral column (Chiralpack IC) and the stability of the enantiomers (barriers of racemisation) was investigated employing chiral HPLC or chiral Dynamic HPLC techniques. A slight influence on the barrier to rotation was noticed when the enantiomerisation was performed in the presence of suitable alkali cations.     

The absolute configuration of angular 3′-acyloxypyranocoumarins by vibrational circular dichroism exciton chirality

A complex mixture of lomatin C-3′ esters and (−)-O-angeloyllomatin 1 was isolated from the seeds of Prionosciadium thapsoides. Since a literature search revealed that some lomatin C-3′ monoesters have positive specific rotations, while others had negative values, the absolute configuration of all of the molecules was determined to be (R) by exciton chirality in the infrared region, and by chemical correlation. A single crystal X-ray study of acetyllomatin 3, using the Flack and Hooft parameters, independently confirmed this absolute configuration.     

Generation of chirality in 4,4′-azopyridine by co-crystallization with optically active dicarboxylic acids

The co-crystals of anti-4,4′-azopyridine apy with optically active 9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid 1 and trans-1,2-cyclohexanedicarboxylic acid 2 were prepared and their solid state CD spectra were measured. The positive Cotton effect sign, corresponding to the lowest energy n–π¹ transition, was correlated with the M helicity of the twisted Ar–NN chromophore. The absolute sense of the twist of the guest apy molecule was deduced from the X-ray structures of the (S,S)-1·apy and (S,S)-2·apy complexes.     

Asymmetric induction by sulfinyl chirality. A total synthesis of (+)-talaromycin A and (−)-talaromycin B

A total synthesis of (+)-talaromycin A and (−)-talaromycin B was accomplished by means of successive asymmetric induction of all chiral centers using a chiral sulfinyl group.     

Enantioselective synthesis of α,β-diamino ester derivatives: memory of chirality in imino-aldol reactions

A simple strategy for the synthesis of chiral α,β-diamino ester derivatives in good yields and ee (up to 92%) utilizing the ‘memory of chirality’ concept is reported. This methodology has been extended for the enantioselective synthesis of substituted aziridines with excellent ee (92%).     

Tris-ACE-(6,6′-bipyridyl)-α-cyclodextrin: synthesis and chirality of the tripodal metal complexes

This Letter describes the synthesis of a C₃-symmetrical tris-^ACE-(6,6′-bipyridyl)-α-CyD via ‘one-pot’ Staudinger-Aza-Wittig reaction (SAW). Metal complexation behavior was investigated by UV–vis and Circular Dichroism. Coordination of 6,6′-bipyridyl units with Cu^II and Ni^II cations, spontaneously generates a strong exciton coupling-type positive Cotton effect proving the formation of a Λ-helix with a left-handed screw propeller (M).     

Highly efficient chirality inducers in nematic liquid crystals: synthesis of 7,7’-disubstituted 2,2’-methylenedioxy-1,1’-binaphthyls

ABSTRACT

We report the synthesis of 7,7?-disubstituted 2,2?-methylenedioxy-1,1?-binaphthyls and demonstrate their application as chiral dopants in the nematic mixture MLC-6260 to produce highly twisted cholesteric phases. Especially mesogenic and/or polarizable groups in the 7,7?-positions of the bridged binaphthyls generate unusually high helical twisting powers.     

Chiral diaminophosphine ligands with stable C(aryl)N(amine) axial chirality derived from prolinol

New type chiral ligands 3, which have a chiral carbon center and stable C(aryl)-N(amine) axial chirality, were prepared from chiral prolinol-derived aminophosphine oxide 4. Pd-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate (6) with a dimethyl malonate-BSA-LiOAc system was successfully carried out in the presence of 3d resulting in a good yield with good enantioselectivity (up to 95% ee).