β-Cyclodextrin Duplexes That Are Connected through Two Disulfide Bonds: Potent Hosts for the Complexation of Organic Molecules

Structural Investigation of Beta-Cyclodextrin Complexes with Cannabidiol and Delta-9-Tetrahydrocannabinol in 1:1 and 2:1 Host-Guest Stoichiometry: Molecular Docking and Density Functional Calculations

The complexation of β-cyclodextrin (β-CD) with cannabidiol (CBD) and Δ⁹-tetrahydrocannabinol (THC) was investigated using molecular docking and M062X/6-31G(d,p) calculations. The calculations suggested two possible complex formations of 1:1 and 2:1 host-guest molecular ratio of β-CD with CBD and THC. The preferred orientation of all complexes in this study exhibited the hydrogen bonding between hydroxy-substituted benzene ring of CBD and THC with the β-CD's secondary hydroxy groups at the wide rim. The calculated complexation energies indicate that formation of the 2:1 complexes (-83.53 to -135.36 kcal/mol) was more energetically favorable and chemically stable than the 1:1 complexes (-30.00 to -34.92 kcal/mol). However, the deformation energies of the host and the guest components in the 2:1 complexes (37.47-96.91 kcal/mol) are much higher than those in the 1:1 complexes (3.49-8.69 kcal/mol), which means the formation processes of the 2:1 complexes are more difficult due to the rigidity of the dimeric β-CDs. Therefore, the inclusion complexes of β-CD with CBD and THC are more likely to be in 1:1 host-guest ratio than in 2:1 molecular ratio. The results of this study supported the experimental results that the complexation constant of 1:1 β-CD/CBD (Ks = 300 M^-1) is greater than that of 2:1 β-CDs/CBD (Kss = 0.833 M^-1). Altogether, this study introduced the fitting parameters that could indicate the stability of the molecular fits in complex formation of each stoichiometry host-guest ratio, which are important for the assessment of the inclusion mechanisms as well as the relationships of reactants and products in chemical reactions.

Programmed Synthesis of Hepta-Differentiated β-Cyclodextrin: 1 out of 117655 Arrangements

Cyclodextrin poly-functionalization has fueled progress in their use in multiple applications such as enzyme mimicry, but also in the polymer sciences, luminescence, as sensors or for biomedical applications. However, regioselective access to a given pattern of functions on β-cyclodextrin is still very limited. We uncover a new orienting group, the thioacetate, that expands the toolbox available for cyclodextrin poly-hetero-functionalization using diisobutylaluminum hydride (DIBAL-H) promoted debenzylation. The usefulness of this group is illustrated in the first synthesis of a precisely hepta-hetero-functionalized β-cyclodextrin. By way of comparison, a random hepta-functionalization would give 117655 different molecules. This synthesis is not simply the vain quest for the Holy Grail of CD hetero-functionalization, but it illustrates the versatility of the DIBAL-H oriented hetero-functionalization strategy, opening the way to a multitude of useful functionalization patterns for new practical applications.

A γ-cyclodextrin duplex connected with two disulfide bonds: synthesis, structure and inclusion complexes

Per(2,3,6-tri-O-benzyl)-γ-cyclodextrin was debenzylated by DIBAL-H to produce a mixture of C6(I),C6(IV) and C6(I),C6(V) isomeric diols, which were separated and isolated. The C2-symmetrical C6(I),C6(V) diol was transformed into dithiol and dimerized to produce a γ-cyclodextrin duplex structure. A crystal structure revealed tubular cavity whose peripheries are slightly elliptically distorted. The solvent accessible volume of the cavity of the γ-CD duplex is about 740 Å(3). Due to this large inner space the duplex forms very stable inclusion complexes with steroids; bile acids examined in this study show binding affinities to the γ-cyclodextrin duplex in the range of 5.3 × 10(7) M(-1)-1.9 × 10(8) M(-1).

Cyclodextrin-peptide conjugates for sequence specific DNA binding

Synthetic models of bZIP transcription factors have been developed with the capability of specific DNA recognition. Our design is based on the CuAAC mediated conjugation of basic region Leucine Zipper peptides to different derivatives of α, β and γ-cyclodextrins equipped with azide functionalities. Thorough optimization of reaction conditions allowed convergent and simultaneous conjugation of two long unprotected cationic peptides to cyclodextrin-bis azide derivatives. The resulting constructs were shown to specifically recognize their cognate DNA sequence with nM affinities. In comparison with previously developed TF models, the derivatives described here combine the enhanced DNA binding capabilities with an easy and convergent synthetic route.

Rapid Macrocycle Threading by a Fluorescent Dye-Polymer Conjugate in Water with Nanomolar Affinity

A macrocyclic tetralactam host is threaded by a highly fluorescent squaraine dye that is flanked by two polyethylene glycol (PEG) chains with nanomolar dissociation constants in water. Furthermore, the rates of bimolecular association are very fast with k(on) ≈ 10(6)-10(7) M(-1) s(-1). The association is effective under cell culture conditions and produces large changes in dye optical properties including turn-on near-infrared fluorescence that can be imaged using cell microscopy. Association constants in water are ∼1000 times higher than those in organic solvents and strongly enthalpically favored at 27 °C. The threading rate is hardly affected by the length of the PEG chains that flank the squaraine dye. For example, macrocycle threading by a dye conjugate with two appended PEG2000 chains is only three times slower than threading by a conjugate with triethylene glycol chains that are 20 times shorter. The results are a promising advance toward synthetic mimics of streptavidin/biotin.

Cyclodextrin capped gold nanoparticles as a delivery vehicle for a prodrug of cisplatin

In this work, we explore the use of a quick coupling mechanism for "arming" a cyclodextrin coated gold nanoparticle (AuNP) delivery vehicle, 2, with an adamantane-oxoplatin conjugate that is a prodrug of cisplatin, 3, to produce a cytotoxic nanodrug, 4. The two-part arming system, which utilizes the well-known guest-host interaction between β-cyclodextrin and adamantane, may be useful for rapidly constituting polyfunctional nanodrugs prior to their application in chemotherapy. The 4.7 ± 1.1 nm delivery vehicle, 2, coated with per-6-thio-β-cyclodextrin (βSCD), was characterized using transmission electron microscopy and absorption spectroscopy, and the density of surface-attached βSCD molecules, ∼210 βSCD/AuNP, was determined using thermogravimetric analysis. Because (13)C NMR spectra of βSCD used in the study exhibited disulfide linkages and the observed surface density on the AuNP exceeded that possible for a close-packed mono layer, a fraction of the surface-attached βSCD molecules on the particle were oligomerized through disulfide linkages. Determination of the binding constant, K, for the 3-βCD interaction using (1)H NMR chemical shifts was complicated by the self-association of 3 to form a dimer through its conjugated adamantane residue. With a dimerization constant of K2 = 26.7 M(-1), the value of K for the 3-βCD interaction (1:1 stoichiometry) is 400-800 M(-1), which is lower than the value, K = 1.4 × 10(3) M(-1), measured for the 2-3 interaction using ICP-MS. Optical microscopy showed that when neuroblastoma SK-N-SH cells are treated with the nanodrug, 4 (2+3), clusters of gold nanoparticles are observed in the nuclear regions of living cells within 24 h after exposure, but, at later times when most cells are dying or dead, clustering is no longer observed. Treating the cells with 4 for 72 h gave percent inhibitions that are lower than that of cisplatin, suggesting that the Pt(IV) ions in 4 may be incompletely reduced to cytotoxic Pt(II) species in the cell.