Allosteric release of cucurbit[6]uril from a rotaxane using a molecular signal.

Rotaxanes can be regarded as storage systems for their wheel components, which broadens their application potential as a complement to the supramolecular systems that retain a mechanically interlocked structure. However, utilising rotaxanes in this way requires a method to release the wheel while preserving the integrity of all molecular constituents. Herein, we present simple rotaxanes based on cucurbit[6]uril (CB6), with an axis equipped with an additional binding motif that enables the binding of another macrocycle, cucurbit[7]uril (CB7).

para-Phenylenediamine Dimer as a Redox-Active Guest for Supramolecular Systems.

Redox-active components are highly valuable in the construction of molecular devices. We combined two p-phenylenediamines (p-PDA) with a biphenyl (BiPhe) unit to prepare a supramolecular guest 4 consisting of three binding sites for cucurbit[7/8]uril (CBn) and/or cyclodextrins (CD). Supramolecular properties of 4 were investigated using NMR, UV-vis, mass spectrometry and isothermal titration calorimetry.

Assembling a supramolecular 3D network with tuneable mechanical properties using adamantylated cross-linking agents and β-cyclodextrin-modified hyaluronan.

Hydrogels based on the supramolecular host-guest concept can be prepared if at least one constituent is a polymer chain modified with supramolecular host or guest (or both) units. Low-molecular-weight multitopic counterparts can also be used, however, guest molecules in the role of cross-linking agents are seldom reported, although such an approach offers wide-ranging possibilities for tuning the system properties via easily achievable structural modifications. In this paper, a series of adamantane-based star-like guest molecules was used for cross-linking of two types of β-cyclodextrin-modified hyaluronan (CD-HA).

Adamantane-Substituted Purine Nucleosides: Synthesis, Host-Guest Complexes with β-Cyclodextrin and Biological Activity.

Purine nucleosides represent an interesting group of nitrogen heterocycles, showing a wide range of biological effects. In this study, we designed and synthesized a series of 6,9-disubstituted and 2,6,9-trisubstituted purine ribonucleosides via consecutive nucleophilic aromatic substitution, glycosylation, and deprotection of the ribofuranose unit. We prepared eight new purine nucleosides bearing unique adamantylated aromatic amines at position 6.

Molecular Rearrangement of Pyrazino[2,3-]quinolin-5(6)-ones during Their Reaction with Isocyanic Acid.

New tetrahydropyrazino[2,3-]quinolin-5(6)-ones were prepared from 3-chloroquinoline-2,4(1,3)-diones and ethylene diamine. In their reaction with HNCO, an unprecedented molecular rearrangement produced new types of hydantoin derivatives. All prepared compounds were characterized on the basis of their H, C, and N NMR and ESI mass spectra and some were authenticated by X-ray analysis of single crystalline material.

Degradation of antibacterial 1-octylpyrrolidin-2-one by bacterial pairs isolated from river water and soil.

The study of bacterial degradation of 1-octylpyrrolidin-2-one (NOP) by river water and soil bacteria was the main aim of the research. Although the compound demonstrated bacteriostatic as well as bactericidal effects against Gram-positive and certain Gram-negative bacteria at concentrations ranging from 100 to 1000 mg L, its concentration of 100 mg L was successfully degraded by microbial communities of both river water and alluvial soil; removal efficiencies reached 87.2 and 88.

Adamantane-Substituted Purines and Their β-Cyclodextrin Complexes: Synthesis and Biological Activity.

Cyclin-dependent kinases (CDKs) play an important role in the cell-division cycle. Synthetic inhibitors of CDKs are based on 2,6,9-trisubstituted purines and are developed as potential anticancer drugs; however, they have low solubility in water. In this study, we proved that the pharmaco-chemical properties of purine-based inhibitors can be improved by appropriate substitution with the adamantane moiety.

Reaction of Tertiary 2-Chloroketones with Cyanide Ions: Application to 3-Chloroquinolinediones.

3-Chloroquinoline-2,4-diones react with cyanide ions in dimethyl formamide to give 3-cyanoquinoline-2,4-diones in small yields due to the strong hindrance of the substituent at the C-3 atom. Good yields can be achieved if the substituent at this position is the methyl group. In the methanol solution, the reaction proceeds by an addition mechanism to form 2-oxo-1a,2,3,7b-tetrahydrooxireno[2,3-c]quinoline-7b-carbonitriles, from which 4-hydroxy-3-methoxy-2-oxo-1,2,3,4-tetrahydroquinoline-4-carbonitriles are subsequently formed by opening of the epoxide ring with methanol.

Modes of Micromolar Host-Guest Binding of β-Cyclodextrin Complexes Revealed by NMR Spectroscopy in Salt Water.

Multitopic supramolecular guests with finely tuned affinities toward widely explored cucurbit[]urils (CBs) and cyclodextrins (CDs) have been recently designed and tested as functional components of advanced supramolecular systems. We employed various spacers between the adamantane cage and a cationic moiety as a tool for tuning the binding strength toward CB7 to prepare a set of model guests with and values of (0.6-5.

A New Hyaluronan Modified with β-Cyclodextrin on Hydroxymethyl Groups Forms a Dynamic Supramolecular Network.

A new hyaluronan derivative modified with β-cyclodextrin units (CD-HA) was prepared via the click reaction between propargylated hyaluronan and monoazido-cyclodextrin (CD) to achieve a degree of substitution of 4%. The modified hyaluronan was characterized by H-nuclear magnetic resonance spectroscopy (NMR) and size exclusion chromatography. Subsequent H-NMR and isothermal calorimetric titration experiments revealed that the CD units on CD-HA can form virtual 1:1, 1:2, and 1:3 complexes with one-, two-, and three-site adamantane-based guests, respectively.

Gas-phase fragmentation of 1-adamantylbisimidazolium salts and their complexes with cucurbit[7]uril studied using selectively H-labeled guest molecules.

Rationale: Bisimidazolium salts (BIMs) represent an interesting family of ditopic ligands that are used in the construction of supramolecular systems with hosts based on cyclodextrins or cucurbit[n]urils. Understanding the fragmentation mechanism of individual BIMs and how this mechanism changes after complexation with cucurbit[n]urils can bring new insight into the intrinsic host-guest relationship, thereby allowing utilization of mass spectrometry to describe binding behavior.

Methods: Selectively H-labeled bisimidazolium salts were prepared and fully characterized by spectroscopic methods.

Cubane Arrives on the Cucurbituril Scene.

Cubane, an intriguing chemical curiosity first studied in the early 1960s, has become a valuable structural motif and has recently been involved in the structures of a great number of prospective compounds. The first dicationic supramolecular guest 5 is prepared and derived from a 1,4-disubstituted cubane moiety, and its binding behavior toward cucurbit[n]urils (CBn) and cyclodextrins (CD) is studied. The bisimidazolium salt 5 forms 1:1 inclusion complexes with CB7, CB8, and β-CD with the respective association constants (6.

Cooperative Binding of Cucurbit[n]urils and β-Cyclodextrin to Heteroditopic Imidazolium-Based Guests.

Imidazolium-based guests containing two distinct binding epitopes are capable of binding β-cyclodextrin and cucurbit[6/7]uril (CB) simultaneously to form heteroternary 1:1:1 inclusion complexes. In the final configuration, the hosts occupy binding sites disfavored in the binary complexes because of the chemically induced reorganization of the intermediate 1:1 aggregate. In addition, the reported guests are capable of binding two CBs to form either 1:2 or 1:1:1 ternary assemblies despite consisting of a single cationic moiety.

Rotaxanes Capped with Host Molecules: Supramolecular Behavior of Adamantylated Bisimidazolium Salts Containing a Biphenyl Centerpiece.

Bisimidazolium salts with one central biphenyl binding site and two terminal adamantyl binding sites form water-soluble binary or ternary aggregates with cucurbit[7]uril (CB7) and β-cyclodextrin (β-CD) with rotaxane and pseudorotaxane architectures. The observed arrangements result from cooperation of the supramolecular stopper binding strength and steric barriers against free slippage of the CB7 and β-CD host molecules over the bisimidazolium guest axle.

N-Benzyl-9-isopropyl-9H-purin-6-amine.

The asymmetric unit of the title compound, C15H17N5, consists of two mol-ecules in which the dihedral angles between the best planes of the purine ring system (r.m.s.

2-Chloro-N-ethyl-9-isopropyl-9H-purin-6-amine.

In the title compound, C(10)H(14)ClN(5), the purine ring system is essentially planar, with an r.m.s.

Determination of intrinsic binding modes by mass spectrometry: gas-phase behavior of adamantylated bisimidazolium guests complexed to cucurbiturils.

Adamantylated bisimidazolium cations exhibit a distinct fragmentation pathway in contrast to their cucurbit[7]uril (CB7) complexes. The observed alternative fragmentation of the guest molecule in a complex clearly correlates to the supposed sterically hindered or allowed slippage of the macrocycle over the axel molecule.

2,6-Dichloro-7-isopropyl-7H-purine.

In the title mol-ecule, C(8)H(8)Cl(2)N(4), the essentially planar imidazole and pyrimidine rings [maximum deviations of 0.0030 (15) and 0.0111 (15) Å, respectively] make a dihedral angle of 1.

(1-Adamant-yl)(3-amino-phen-yl)methanone.

In the crystal sructure of the title compound, C(17)H(21)NO, the mol-ecular packing is stabilized by inter-molecular N-H⋯O hydrogen bonds and additional weak N-H⋯π inter-actions, forming chains that propagate along the b axis. Conjugation of the carbonyl group and the benzene ring is rather attenuated due to a twisting of the carbonyl group from the plane of the benzene ring [torsion angle = 27.1 (2)°].

2-(1-Adamant-yl)-1-(3-amino-phen-yl)ethanol.

In the crystal structure of the title compound, C(18)H(25)NO, mol-ecules are linked via O-H⋯N hydrogen bonds, forming chains parallel to the c axis. Additional weak N-H⋯O inter-actions stabilize the crystal packing. The adamantane cage consists of three fused cyclo-hexane rings in almost ideal chair conformations, with C-C-C angles in the range 107.

1-(Bromo-meth-yl)adamantane.

The title compound, C(11)H(17)Br, has crystallographically imposed mirror symmetry in the solid state with mol-ecules bis-ected by mirror planes parallel to the crystallographic ac plane (five C atoms, three H atoms and the Br atom lie on the mirror plane). The asymmetric unit contains one half-mol-ecule. The crystal packing is stabilized only via weak non-specific van der Waals inter-actions.

1-Adamantylmethyl 2-amino-benzoate.

The asymmetric unit of the title compound, C(18)H(23)NO(2), consists of two crystallographically independent mol-ecules bearing an adamantane cage consisting of three fused cyclo-hexane rings in almost ideal chair conformations, with C-C-C angles in the range 108.47 (16)-110.59 (15)°.

1-(2-Phenyl-eth-yl)adamantane.

In the title compound, C(18)H(24), the adamantane cage consists of three fused cyclo-hexane rings in almost ideal chair conformations, with C-C-C angles in the range 108.0 (14)-111.1 (15)°.