Chiral recognition of carboxylic acids by Tröger’s base derivatives

Chiral Recognition and Resolution of Phosphoric Acids Using Octahedral Cobalt Complexes

Determining the chirality of phosphoric acids can be a challenging task. In this study, we present a novel approach for the chiral recognition of phosphates using cationic octahedral cobalt complexes. By utilizing ³¹P NMR spectroscopy, we are able to accurately measure the enantiopurities of chiral phosphoric acids after forming ion pairs with the cobalt complexes. We have successfully applied this method to a variety of chiral phosphoric acids derived from BINOL, H8-BINOL, SPINOL, VAPOL, and VANOL compounds, as well as ATP, and were able to efficiently resolve them in ³¹P{¹H} NMR spectra. Furthermore, we were able to achieve an optical resolution of a phosphoric acid with an enantiomeric excess of greater than 99%.

Synthesis and intramolecular ring transformation of N,N'-dialkylated 2,6,9-triazabicyclo[3.3.1]nonadienes

The first and facile synthesis of N,N'-dialkylated 2,6,9-triazabicyclo[3.3.1]nonadienes was achieved by the [4 + 4] self-condensation of β-formyl-β-nitroenamine in the presence of ammonium acetate. The 2,6- and 2,9-dialkylated products were found to be interconvertible when dissolved in a solvent. This isomerization proceeds through intramolecular ring transformation via a common intermediate under equilibrium.

Glycoconjugates Based on Supramolecular Tröger's Base Scaffold: Synthesis, Photophysics, Docking, and BSA Association Study

This study presents new Tröger's bases bearing glycosyl moieties obtained from a copper-catalyzed azide-alkyne cycloaddition reaction. The Tröger's bases present absorption maxima close to 275 nm related to fully spin and symmetry-allowed electronic transitions. The main fluorescence emission located at 350 nm was observed with no influence on the glycosyl moieties. Furthermore, protein detection studies have been performed using bovine serum albumin (BSA) as a model protein, and results have shown a strong interaction between some of the compounds through a static fluorescence suppression mechanism related to the formation of a glycoconjugate-BSA complex favored by the glycosyl subunit. Moreover, docking was also studied for better understanding the suppression mechanism and indicated that the glycosyl and triazole moieties increase the affinity with BSA.

Hünlich base derivatives as photo-responsive Λ-shaped hinges

The azo derivatives of the Hünlich base are introduced as a set of molecular switches with unique shapes and properties.

One-pot facile synthesis of 4-amino-1,8-naphthalimide derived Tröger's bases via a nucleophilic displacement approach

We report here a novel one-pot synthetic strategy for the synthesis of a family of N-alkyl-1,8-naphthalimide derived Tröger's bases (in overall yield of 65–96%) via a nucleophilic substitution reaction.

Crystal structure of 1,1′-diformyl-4,4′-(6H,12H-5,11-methano-dibenzo[b,f][11,5]diazocine-2,8-diyl)dibenzene, C29H22N2O2

C29H22N2O2, triclinic, P1̅ (no. 2), a = 22.4995(6) Å, b = 9.9370(3) Å, c = 21.6466(6) Å, β = 115.941(1)°, V = 4352.1(2) Å3, Z = 4, R gt (F) = 0.0487, wR ref (F 2 ) = 0.1473, T = 296 K.

Synthesis of Tertiary and Quaternary Amine Derivatives from Wood Resin as Chiral NMR Solvating Agents

Chiral tertiary and quaternary amine solvating agents for NMR spectroscopy were synthesized from the wood resin derivative (+)-dehydroabietylamine (2). The resolution of enantiomers of model compounds [Mosher’s acid (3) and its n-Bu₄N salt (4)] (guests) by (+)-dehydroabietyl-N,N-dimethylmethanamine (5) and its ten different ammonium salts (hosts) was studied. The best results with 3 were obtained using 5 while with 4 the best enantiomeric resolution was obtained using (+)-dehydroabietyl-N,N-dimethylmethanaminium bis(trifluoromethane-sulfonimide) (6). The compounds 5 and 6 showed a 1:1 complexation behaviour between the host and guest. The capability of 5 and 6 to recognize the enantiomers of various α-substituted carboxylic acids and their n-Bu₄N salts in enantiomeric excess (ee) determinations was demonstrated. A modification of the RES-TOCSY NMR pulse sequence is described, allowing the enhancement of enantiomeric discrimination when the resolution of multiplets is insufficient.

Synthesis of chiral 2,3-disubstituted 1,4-diazabicyclo[2.2.2]octane derivatives

Racemic 2,3-diaryl-1,4-diazabicyclo[2.2.2]octane (DABCO) derivatives are synthesized from the readily accessible piperazines in 50-64% yield by cyclization using ethylene bromide, triethylamine, and KI at 80 °C. The enantiomerically enriched 2,3-diphenylpiperazine and the 2,3-bis(1-naphthyl)piperazine derivatives are prepared by a resolution method using commercially available optically active acids, yielding the corresponding DABCO derivatives in 51-64% yield with up to 99% ee. This mild cyclization can also be applied to enantiopure camphanyldiamine derivatives, and the products are obtained in 72-86% yields.

Design and synthesis of Tröger's base ditopic receptors: host-guest interactions, a combined theoretical and experimental study

Two flexible Tröger's base ditopic receptors C4TB and C5TB incorporating monoaza crown ether were designed and synthesized for bisammonium ion complexation. A comprehensive study of host-guest interactions was established by (1)H NMR spectroscopy and DFT calculations. Bisammonium chloride (A1) with a shorter alkyl chain spacer showed the highest affinity for the receptors. M06-2X/cc-pVTZ calculations including the solvent effects on host-guest complexes were employed to explain and rationalize the experimental trends. The short N-H···O or N-H···N hydrogen-bond distances observed in the range of 1.71-1.98 Å indicate the existence of a strong charge assisted hydrogen bonding between the host and the guest. The unusual behaviour (higher binding constant) of A5 in (1)H NMR titration is traced to the conformational folding of the guest.

Synthesis and applications of secondary amine derivatives of (+)-dehydroabietylamine in chiral molecular recognition

(+)-Dehydroabietylamine (1a), the novel derivatives (2a–6a) and their NTf₂ salts (1b–6b) were tested as chiral NMR solvating agents for the resolution of enantiomers of Mosher's acid and other carboxylic acids, and their n-Bu₄N salts.

Facile access to imidazole and imidazolium substituted dibenzo-diazocines

The C₂-symmetrical 2,8- and 4,10-diimidazo methano dibenzo diazocines were synthesized and converted into alkyl imidazolium salts.

Theoretical investigation of Raman optical activity signatures of Tröger's base

The Raman and VROA spectra of (S,S)-Tröger's base are simulated. We mainly discuss the peaks in the 1140-1400 cm(-1) wavenumber range where an intense VROA signature is found. In this range, nearly all of the Raman-active bands belong to the irreducible representation A (C(2) point group), whereas no such observation is made for the VROA spectrum. The vibrational normal modes associated with the peaks in this range mainly consist of wagging and twisting motions of the hydrogen atoms. From the atomic contribution patterns (ACPs) and the group coupling matrices (GCMs), one finds that the VROA backward-scattering intensities mainly arise from hydrogen and carbon atoms in the vicinity of the two chiral nitrogen atoms. The VROA signatures in the 1140-1400 cm(-1) range are therefore a fingerprint of the local chirality around the two chiral nitrogen centers.

Stereoselective synthesis of configurationally stable functionalized ethano-bridged Tröger bases

New functionalized ethano-bridged Tröger bases are readily prepared using a simple alkylation/rearrangement sequence which affords configurationally stable derivatives as single stereoisomers (de > 96%).