Guest-Facilitated Heteroleptic Assembly of Helical Anionocages Enables Reversible Chirality Modulation.

We report a novel strategy for reversible modulation of the supramolecular chirality based on guest-facilitated heteroleptic assembly of helical anionocages. Two triple-stranded helical anionocages including a chiral cage 1 (A2 L1 3 ) and a crown ether functionalized achiral cage 2 (A2 L2 3 ) were synthesized by anion coordination of bis-monourea-based ligands and PhPO3 2- . Both cages exhibited favorable binding with tetraethylammonium TEA+ and cobaltocenium Cob+ (endo-guest, bound in the cavity). Additionally, cage 2 could reversibly release and recapture the guests through binding the exo-guest potassium ions (K+ ) in the crown ethers and subsequent removal of the K+ by [2,2,2]-cryptand. The circular dichroism (CD) spectrum of cage 1 was not significantly affected by guest encapsulation or mixing with the "empty" cage 2. However, in the presence of both cage 2 and an endo-guest/exo-guest, the Cotton effects were reversed at 391 nm and significantly enhanced at 310 nm. This observation was attributed to the guest-facilitated formation of heteroleptic cages that enabled effective chirality transfer from the chiral to the achiral ligands. The CD changes induced by K+ could be fully reversed by removing it with [2,2,2]-cryptand. Sequential addition and removal of K+ allowed reversible modulation of the chirality for at least 10 cycles without significant attenuation.

Stereoselective Assembly of Hydrogen-Bonded Anionic Cages Dictated by Organophosphate-Based Chiral Nodes.

Inspired by the signal transduction function of organophosphates in biological systems, bioactive organophosphates were utilized for the first time as chiral nodes to dictate the stereoselective assembly of hydrogen-bonded anionic cages. Phosphonomycin (antibiotics), tenofovir (antivirals), adenosine monophosphate (natural product, AMP) and clindamycin phosphate (antibiotics) were assembled with an achiral bis-monourea ligand, thereby leading to the stereoselective formation of quadruple or triple helicates. The extent of the stereoselectivity could be enhanced by either lowering the temperature or adding stronger-binding cations as templates. With the chiral anionic cages as the host, some enantioselectivity was achieved when binding chiral quaternary ammonium cations.

Less is More: A Shortcut for Anionocages Design Based on (RPO3 2- )-Monourea Coordination.

Anionocages have been developed as a unique family of hydrogen bonded cages. However, strategies for constructing anionocages are mainly limited to that based on (PO4 3- )-bisurea coordination, neither the ligands nor the anions lack the simplicity and diversity of the maturely developed analogues based on metal coordination (i.e. metallocage). We report herein a more simple strategy for anionocages design based on (RPO3 2- )-monourea coordination, utilizing monourea rather than bisurea as the hydrogen binding donor, and RPO3 2- rather than PO4 3- as the acceptor. Two fluorescent, quadruple helicate anionocages were constructed by a bis-monourea ligand, and dianions PhOPO3 2- (H1 ) or HOPO3 2- (H1A ), respectively, which were capable of encapsulating a series of cation guests. As revealed by molecular modeling, H1 features remarkable guest-adaptive cavity breathing without change of the quadruple helicate topology, which allowed the encapsulation of different sized guests in an "induced fit" manner.

Crown Ether Functionalized Potassium-Responsive Anionocages for Cascaded Guest Delivery.

In many critical biological processes, host-guest chemistry of protein receptors is regulated by effector molecules to realize cascaded delivery of messenger molecules between different targets. Mimicking these natural processes with artificial receptors remains a challenge. Herein, we report a cascaded guest delivery between two anionocages (anion-coordination-driven cages), in a reversible manner, wherein binding of K+ ions by a crown ether functionalized, heteroleptic A2 L3 (A=anion, L=ligand) anionocage triggers the release and delivery of a TEA+ (tetraethylammonium) guest to another A2 L3 anionocage that is a weaker and less K+ -sensitive receptor. Elimination of the K+ with [2,2,2]-cryptand enables recapture of the TEA+ by the crown ether functionalized anionocage and thus realizes a reversed guest delivery. Moreover, integrative self-sorting of anionocages is firstly reported, leading to heteroleptic cages with enhanced guest binding affinities.

Peripheral Templation-Modulated Interconversion between an A4 L6 Tetrahedral Anion Cage and A2 L3 Triple Helicate with Guest Capture/Release.

An anion-coordination-based A4 L6 ("A" denotes anion and "L" is ligand) tetrahedral cage was constructed by a C2 -symmetric bis-bis(urea) ligand and phosphate anion, which showed reversible interconversion with the A2 L3 triple helicate as a response to the template, concentration, or solvent. Notably, an unusual "peripheral" templation was found to be critical to stabilize the tetrahedral structure. This peripheral effect was utilized to assemble an "empty" A4 L6 cage that allows the multi-stimuli-controlled capture/release of biologically important species such as choline and acetylcholine.

Chelate effects in sulfate binding by amide/urea-based ligands.

The influence of chelate and mini-chelate effects on sulfate binding was explored for six amide-, amide/amine-, urea-, and urea/amine-based ligands. Two of the urea-based hosts were selective for SO4(2-) in water-mixed DMSO-d6 systems. Results indicated that the mini-chelate effect provided by a single urea group with two NH binding sites appears to provide enhanced binding over two amide groups. Furthermore, additional urea binding sites incorporated into the host framework appeared to overcome to some extent competing hydration effects with increasing water content.

De novo structure-based design of ion-pair triple-stranded helicates.

We present a generalized approach toward the design of ion-pair ML3A helicates assembled by coordination of metal cations (M) and anions (A) by ditopic chelating ligands (L). This computational approach, based on de novo structure-based design principles implemented in the HostDesigner software, led to identification of synthetically accessible ditopic ligands that are structurally encoded to form charge-neutral ion-pair helicates with FeSO4 or LnPO4.

Stepwise encapsulation of sulfate ions by ferrocenyl-functionalized tripodal hexaurea receptors.

Three ferrocenyl-functionalized tripodal hexaurea anion receptors with ortho- (L(2)), meta- (L(3)), and para-phenylene (L(4)) bridges, which showed strong binding affinities toward sulfate ions, have been designed and synthesized. In particular, meta-phenylene-bridged ligand L(3), owing to its trigonal bipyramidal structure, can encapsulate two SO4(2-) ions in its "inner" and "outer" tripodal clefts, respectively, as supported by their clearly distinct NMR resonances and by molecular modeling. The sulfate complex of ortho-ligand L(2), (TBA)2[SO4⊂L(2)]·2H2O (1), displays a caged tetrahedral structure with an encapsulated sulfate ion that is hydrogen bonded by the six urea groups of ligand L(2). CV studies showed two types of electrochemical response of the ferrocene/ferrocenium redox couple upon anion binding, that is, a shift of the wave and the appearance of a new peak. Quantitative binding data were obtained from the NMR and CV titrations.

Pharmacokinetic Interactions and Tolerability of Rosuvastatin and Ezetimibe: A Randomized, Phase 1, Crossover Study in Healthy Chinese Participants.

BACKGROUND AND OBJECTIVE: The combination of rosuvastatin and ezetimibe has promising clinical benefits with a significant safety and tolerability profile. However, there is a lack of clinical data supporting the drug-drug interaction (DDI) in Chinese population. Thus, the aim of this study is to assess the potential pharmacokinetic DDI between rosuvastatin and ezetimibe in a Chinese population. METHODS: In this randomized, open-label, phase 1 study, 12 healthy volunteers were randomized to three treatment groups: 10 mg rosuvastatin plus 10 mg ezetimibe, 10 mg rosuvastatin alone, and 10 mg ezetimibe alone under fasting conditions. The plasma concentrations of rosuvastatin and ezetimibe were determined, and the pharmacokinetic parameters were calculated. Primary endpoints were peak plasma concentration (Cmax), area under the curve from zero to last measurement (AUC0-t), and area under the curve from zero to infinity (AUC0-∞) that were log-transformed, and co-administration was compared with monotherapy to evaluate the DDI. RESULTS: The geometric mean ratios (GMRs) of rosuvastatin with 90% confidence intervals (CIs) were 0.94 (0.80-1.12) for Cmax, 0.96 (0.85-1.08) for AUC0-t, and 0.96 (0.86-1.07) for AUC0-∞ when administered in combination with ezetimibe versus administered alone. The GMRs of unconjugated ezetimibe and total ezetimibe with 90% CIs were 1.15 (1.00-1.32) and 0.93 (0.80-1.07) for Cmax, 0.96 (0.84-1.10) and 0.95 (0.83-1.08) for AUC0-t, and 1.06 (0.96-1.18) and 0.94 (0.80-1.11) for AUC0-∞, respectively, when administered in combination with rosuvastatin versus administered alone. CONCLUSION: Co-administration of rosuvastatin and ezetimibe showed no clinically significant pharmacokinetic interactions in a healthy Chinese population.

A Bioequivalence Study of Ezetimibe/Rosuvastatin Fixed Dose Combination (10 mg/10 mg) Versus the Individual Formulations Taken Concomitantly.

INTRODUCTION: This study evaluated the bioequivalence of ezetimibe/rosuvastatin fixed dose combination compared to the concomitant administration of individual formulations (ezetimibe and rosuvastatin) in Chinese healthy subjects under fasting conditions. METHODS: This was a phase I, randomized, open-label, two-treatment, two-period, two-sequence, crossover study conducted in healthy Chinese participants under fasting conditions. Cmax, AUC0-t, and AUC0-∞ from test and individual reference formulations were evaluated to assess bioequivalence. The safety assessments included adverse events (AEs)/treatment-emergent adverse events (TEAEs), potential clinically significant abnormalities (PCSAs) in vital signs, 12-lead electrocardiogram (12-ECG), and clinical laboratory parameters. RESULTS: Of the 68 subjects enrolled, 67 were treated. Systemic exposure to rosuvastatin based on Cmax, AUC0-t, and AUC0-∞ was similar in both treatments, with respective arithmetic values 12.4 ng/ml, 117 ng·h/mL, and 120 ng·h/mL for test formulation and 12.7 ng/ml, 120 ng·h/mL, and 123 ng·h/mL for reference formulations. Similarly, systemic exposure to unconjugated ezetimibe was 4.14 ng/ml, 89.7 ng·h/mL, and 102 ng·h/mL for the test formulation and 3.80 ng/ml, 89.7 ng·h/mL, and 102 ng·h/mL for reference formulations. Systemic exposure to total ezetimibe was 70.5 ng/ml, 664 ng·h/mL, and 718 ng·h/mL for test formulation and 60.2 ng/ml, 648 ng·h/mL, and 702 ng·h/mL for reference formulations. The point estimates for rosuvastatin unconjugated ezetimibe and total ezetimibe were in the acceptable range of 0.80-1.25. No deaths or serious adverse events were reported. CONCLUSIONS: Fixed dose combination of ezetimibe/rosuvastatin (10 mg/10 mg) achieved bioequivalence with reference to commercial tablets. TRIAL REGISTRATION NUMBER: CTR20202108.

Anion-dependent formation of helicates versus mesocates of triple-stranded M2L3 (M = Fe2+, Cu2+) complexes.

A series of dinuclear triple-stranded complexes, [Fe(2)L(3)⊃X]X(6) [X = BF(4)(-) (1), ClO(4)(-) (2)], [Fe(2)L(3)⊃SO(4)](2)(SO(4))(5) (3), [Fe(2)L(3)⊃Br](BPh(4))(6) (4), Fe(2)L(3)(NO(3))Br(6) (5), and [Cu(2)L(3)⊃NO(3)](NO(3))(6) (6), which incorporate a central cavity to encapsulate different anions, have been synthesized via the self-assembly of iron(II) or copper(II) salts with the N,N'-bis[5-(2,2'-bipyridyl)methyl]imidazolium bromide (LBr) ligand. X-ray crystallographic studies (for 1-4 and 6) and elemental analyses confirmed the cagelike triple-stranded structure. The anionic guest is bound in the cage and shows remarkable influence on the outcome of the self-assembly process with regard to the configuration at the metal centers. The mesocates (with different configurations at the two metal centers) have formed in the presence of large tetrahedral anions, while helicates (with the same configuration at both metal centers) were obtained when using the relatively smaller spherical or trigonal-planar anions Br(-) or NO(3)(-).

An electrochemical and optical anion chemosensor based on tripodal tris(ferrocenylurea).

A neutral tripodal tris(ferrocenylurea) anion receptor has been designed that can electrochemically and optically recognize sulfate and phosphate anions. The binding of the tetrahedral anion induced distinct cathodic shifts of the ferrocene/ferrocenium redox couple in chloroform, whereas the UV/Vis spectrum of the receptor showed an increase in the d-d transition band upon addition of sulfate ions. Furthermore, the anion complexes (TBA)2 · [SO4 ⊂L] · H2O (1) and TBA[F⊂L] (2; TBA = tetrabutylammonium ion) were isolated. Crystal structural analyses showed that the receptor in the two 1:1 (host/guest) complexes encapsulated sulfate or fluoride ions in the tripodal cavity through multiple hydrogen bonds. (1)H NMR spectroscopic and ESI mass-spectrometric analysis revealed strong sulfate and fluoride binding in solution.

Redox-driven sulfate ion transfer between two tripodal tris(urea) receptors.

Two anion receptors with the same tripodal scaffold but different signaling groups are employed to control intermolecular anion transfer via an electrochemical stimulus, which is detected by the change of the fluorescence intensity before and after electrochemical oxidation of the ferrocenyl units.

A colorimetric and ratiometric fluorescent chemosensor for fluoride based on proton transfer.

N-Phenyl-N'-(3-quinolinyl)urea (1) has been developed as a highly selective colorimetric and ratiometric fluorescent chemosensor for fluoride ion based on a proton transfer mechanism. Evidences for the mechanism were provided by UV-vis and fluorescence titration and especially (1)H and (19)F NMR experiments. The sensor gave the largest ratiometric fluorescent response reported so far (R(max)/R(min) = 2620) to fluoride. Taking H(+) as the "recovering reagent", the sensor can be reversibly "used" and "recovered" for several cycles with only a slight decay of the response ability.

Full- or half-encapsulation of sulfate anion by a tris(3-pyridylurea) receptor: effect of the secondary coordination sphere.

Self-assembly of the [Fe(DABP)(3)]SO(4) (DABP = 5,5'-diamino-2,2'-bipyridine) or [Fe(bipy)(3)]SO(4) (bipy = 2,2'-bipyridine) complex with a tripodal tris(3-pyridylurea) ligand (L) results in a layered structure that includes a sulfate anion in the cleft of one L molecule. The two compounds, [Fe(DABP)(3)][SO(4) L] x 10 H(2)O (2) and [Fe(bipy)(3)][SO(4) L] x 9 H(2)O (3), show very similar sheets formed by the anionic units [SO(4) L](2-) and cationic building blocks ([Fe(DABP)(3)](2+) or [Fe(bipy)(3)](2+)). However, there are different water clusters that link the adjacent layers in the two products, that is, water parallelograms and quasi "water cubes" in 2 versus single water molecules, water dimers, and hexamers in 3. The half-encapsulation of sulfate by a single L molecule contrasts with the previously reported full-encapsulation of the sulfate ion by two L molecules in [M(H(2)O)(6)][SO(4) L(2)] (1). This different anion encapsulation is traced to the hydrogen-acceptor properties of the pyridyl groups of L together with the hydrogen-bonding properties of the cation secondary coordination sphere for a solid-state packing optimization. In 1 the direct hydrogen bonding from the secondary coordination sphere of octahedral [M(H(2)O)(6)](2+) to L-pyridyl helps in the formation of an octahedral cation-anion coordination in the NaCl-type structure. In 2 and 3, crystal water instead of the cations has to satisfy the hydrogen-accepting demands of L. Consequently, a non-spherical and only partly water-surrounded half-encapsulated [SO(4) L](2-) anion allows for a closer approach of the [Fe(DABP)(3)](2+) or [Fe(bipy)(3)](2+) cations than the [SO(4) L(2)](2-) anion. Then, the similar cation and anion size in 2 and 3 with the Coulomb attraction confined to a two-dimensional plane leads to the formation of a hexagonal BN (or graphite) lattice. Competition experiments with different anions for compound 2 reveal that SO(4)(2-) can be selectively crystallized against NO(3)(-), OAc(-), or ClO(4)(-).

Selective binding of (thio)sulfate and phosphate in water by quaternary ammonium functionalized oligo-ureas.

Recognition of (thio)sulfate and phosphate in aqueous solutions has been demonstrated by using oligo-urea-based receptors functionalized with quaternary ammonium groups. The ammonium groups allow for increased aqueous solubility while simultaneously providing positive coulombic interactions and stronger hydrogen bonding through an inductive effect. This simple and generally applicable modification provides an effective way to bolster the anion binding and water solubility of oligo-urea-based receptors. With a water soluble receptor 2, selective binding of adenosine phosphates was achieved at physiological pH.

Selective recognition of choline phosphate by tripodal hexa-urea receptors with dual binding sites: crystal and solution evidence.

Two tripodal hexa-urea receptors functionalized with aromatic terminal groups are capable of binding choline phosphate (CP). Crystal structures of the host-guest complexes reveal that the zwitterion CP is efficiently encapsulated in the tripodal hosts in a dual-site binding mode. The phosphate tail of CP is coordinated by the urea groups and the quaternary ammonium head is bound in a 'composite aromatic box' through cation-π and hydrogen-bonding interactions. Such a partial aromatic binding environment for the Me3N-+ cation mimics that of most enzymes catalyzing the conversion of quaternary ammonium substrates. Moreover, NMR, ESI-MS, and fluorescence studies demonstrate the selective binding and sensing of CP over other competing species such as ADP, ATP, choline and derivatives.

Sulfate ion encapsulation in caged supramolecular structures assembled by second-sphere coordination.

A tripodal tris(3-pyridylurea) receptor (L) assembles with metal sulfate salts MSO(4) (M=Mn, Zn) to afford supramolecular cages [SO(4) subset L(2)] that encapsulate the SO(4)(2-) ion via multiple hydrogen bonds in a three-dimensional structure held by second-sphere coordination; (1)H NMR and negative-ion mode ESI-MS spectra reveal significantly strong sulfate binding in solution.

Chirality sensing of choline derivatives by a triple anion helicate cage through induced circular dichroism.

Chirality sensing of choline derivatives is achieved by a self-assembled, racemic triple anion helicate cage which exhibits induced circular dichroism (ICD) upon encapsulation of a chiral guest. The host-guest interactions were illustrated by NMR, crystal structure, CD and DFT calculations. The absolute configurations and ee values were determined by ICD.

Selective binding of choline by a phosphate-coordination-based triple helicate featuring an aromatic box.

In nature, proteins have evolved sophisticated cavities tailored for capturing target guests selectively among competitors of similar size, shape, and charge. The fundamental principles guiding the molecular recognition, such as self-assembly and complementarity, have inspired the development of biomimetic receptors. In the current work, we report a self-assembled triple anion helicate (host 2) featuring a cavity resembling that of the choline-binding protein ChoX, as revealed by crystal and density functional theory (DFT)-optimized structures, which binds choline in a unique dual-site-binding mode. This similarity in structure leads to a similarly high selectivity of host 2 for choline over its derivatives, as demonstrated by the NMR and fluorescence competition experiments. Furthermore, host 2 is able to act as a fluorescence displacement sensor for discriminating choline, acetylcholine, L-carnitine, and glycine betaine effectively.The choline-binding protein ChoX exhibits a synergistic dual-site binding mode that allows it to discriminate choline over structural analogues. Here, the authors design a biomimetic triple anion helicate receptor whose selectivity for choline arises from a similar binding mechanism.