Intramolecular Hydrogen Bond Research Articles

Theoretical Study on the Effect of Cyano- and Dimethylamine-Group on ESIPT Behavior and Luminescent Properties of Novel Flavone-Based Fluorophore.

Recently, a new fluorescent senor based on 3-hydroxy-2-(naphthalen-2-yl)-4H-chromen-4-one (HFN) for selective detection of H2Sn was obtained in the experiment (Spectrochim. Acta Part A 271(2022)120962). Based on HFN, three new compounds (HFN1, HFN2 and HFN3) are designed to explore the influences of dimethylamine (-N(CH3)2) and cyano (-CN) groups on the excited-state intramolecular proton transfer (ESIPT) process and luminescent features of HFN. After analyzing the mainly geometrical parameters, electron densities and infrared spectra, we discovered that the intramolecular hydrogen bonds (IHBs) in the target molecules become stronger upon photo-excitation. Introducing -CN or/and -N(CH3)2 groups into HFN indeed influences its ESIPT behavior and luminescent properties. The -N(CH3)2 group enhances IHB, reduces ESIPT barrier and caused absorption/ fluorescence (at T form) peak blue-shift, while the -CN group shows a counterproductive effect. The coincidence of -N(CH3)2 and -CN made the absorption/fluorescent wavelength of HFN red-shift more than single -N(CH3)2 or -CN group does.

Theoretical investigation of the excited-state intramolecular double proton transfer process of 2,2'-(benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diyl)diphenol.

In this work, the excited state intramolecular double proton transfer (ESIDPT) mechanism of 2,2'-(benzo[1,2-d:4,5-d']bis(thiazole)-2,6-diyl)diphenol (BTAP) is proposed using density functional theory (DFT) and time-dependent DFT (TDDFT). The changes in bond lengths, bond angles and IR vibrational spectra associated with two intramolecular hydrogen bonds of BTAP upon photoexcitation indicate that the hydrogen bonds are strengthened in the excited state, facilitating the ESIDPT process. Investigation of the constructed S1-state potential energy surface proposes that BTAP prefers a stepwise ESIDPT mechanism. Electronic spectra and frontier molecular orbitals (FMOs) are also presented to illustrate the luminescent properties of BTAP.

Redox-active chemical chaperones exhibiting promiscuous binding promote oxidative protein folding under condensed sub-millimolar conditions.

Proteins form native structures through folding processes, many of which proceed through intramolecular hydrophobic effect, hydrogen bond and disulfide-bond formation. In vivo, protein aggregation is prevented even in the highly condensed milieu of a cell through folding mediated by molecular chaperones and oxidative enzymes. Chemical approaches to date have not replicated such exquisite mediation. Oxidoreductases efficiently promote folding by the cooperative effects of oxidative reactivity for disulfide-bond formation in the client unfolded protein and chaperone activity to mitigate aggregation. Conventional synthetic folding promotors mimic the redox-reactivity of thiol/disulfide units but do not address client-recognition units for inhibiting aggregation. Herein, we report thiol/disulfide compounds containing client-recognition units, which act as synthetic oxidoreductase-mimics. For example, compound βCDWSH/SS bears a thiol/disulfide unit at the wide rim of β-cyclodextrin as a client recognition unit. βCDWSH/SS shows promiscuous binding to client proteins, mitigates protein aggregation, and accelerates disulfide-bond formation. In contrast, positioning a thiol/disulfide unit at the narrow rim of β-cyclodextrin promotes folding less effectively through preferential interactions at specific residues, resulting in aggregation. The combination of promiscuous client-binding and redox reactivity is effective for the design of synthetic folding promoters. βCDWSH/SS accelerates oxidative protein folding at highly condensed sub-millimolar protein concentrations.

Effect of sugar or sugar alcohol with different spatial structures on the stability of paclitaxel/HS15/Tween80 micelles: Based on micellization thermodynamics

Paclitaxel (PTX) is clinically recommended for the treatment of breast, ovarian and non-small cell lung cancer. This study delves into the impact of sugars (mannose or glucose) and sugar alcohols (mannitol or sorbitol) with varying spatial structures on the interfacial and thermodynamic behavior of the PTX/HS15/Tween80 micellar system. The research reveals that the presence of OH groups in sugars and sugar alcohols enhances hydrogen bonding force between surfactant and water, altering the critical micelle concentration (CMC) in solution and the surfactant’s arrangement at the interface, thus facilitating micelle formation and enhancing system stability. Dynamic light scattering (DLS) results show that the particle size of the PTX/HS15/Tween80 system is 11.69 nm, with micellar size showing a positive correlation with additive concentration. Sugar alcohols exhibit a more pronounced effect on increasing micelle size compared to sugars. Molecules featuring outward-facing OH groups demonstrating a greater ability to facilitate the formation of smaller micelle than those with inward-facing groups, emphasizing the influence of spatial structural differences. Stability experiments demonstrate that light transmission remains above 97 % in the system for 8 h after the addition of sugar, and the relative absorbance of PTX is maintained above 97 % within 6 h. Results from FD-B21 fluorescence probe release further confirm the positive impact of sugars and sugar alcohols on the stability of PTX/HS15/Tween80 micelles, highlighting stability differences based on molecules with distinct spatial structures. When OH groups on sugar or sugar alcohol molecules are more oriented in the same direction, intramolecular hydrogen bonds are formed, reducing spatial resistance and promoting the formation of micellar with smaller particle sizes. This process enhances physical stability by reducing inter-molecular collisions. In summary, the presence of sugars and sugar alcohols promotes micelle formation and boosts system stability, offering valuable insights for enhancing the stability of drug-loaded micelles.

Antioxidation Activity Enhancement by Intramolecular Hydrogen Bond and Non-Browning Mechanism of Active Ingredients in Rosemary: Carnosic Acid and Carnosol.

Rosemary is one of the most promising, versatile, and studied natural preservatives. Carnosic acid (CA) and carnosol (CARN), as the primary active ingredients of rosemary extracts, have little difference in structure, but their antioxidant activities vary significantly, depending on the system studied. The underlying molecular mechanisms remain unclear. By means of optical spectroscopies, stopped-flow, laser photolysis, and density functional theory (DFT) calculations, we have compared CA and CARN between their reaction dynamics of radical scavenging, metal ion chelation, and oxidation inhibition in lipid emulsion and beef, as well as between their interactions with β-carotene (β-Car). For reference, 3-isopropyl catechol (IC), which is structurally similar to the active groups of CA and CARN, was studied in parallel. It is found for CA that the intramolecular hydrogen bond can boost the acidity of its phenol hydroxyl and that the synergistic effect with β-Car can substantially enhance its antioxidation activity in the model systems of lipid and meat via the CA-to-β-Car electron transfer reaction. The substitution of A and B rings on the catechol group in both CA and CARN limits browning caused by their formation of oxidative products as antioxidants.

Crystalline Porous Organic Cage Membranes Constructed Using Fortified Intermolecular Interactions for Molecular Sieving.

Among the various types of materials with intrinsic porosity, porous organic cages (POCs) are distinctive as discrete molecules that possess intrinsic cavities and extrinsic channels capable of facilitating molecular sieving. However, the fabrication of POC membranes remains highly challenging due to the weak noncovalent intermolecular interactions and most reported POCs are powders. In this study, we constructed crystalline free-standing porous organic cage membranes by fortifying intermolecular interactions through the induction of intramolecular hydrogen bonds, which was confirmed by single-crystal X-ray analysis. To elucidate the driving forces behind, a series of terephthaldehyde building blocks containing different substitutions were reacted with flexible triamine under different conditions via interfacial polymerization (IP). Furthermore, density functional theory (DFT) calculations suggest that intramolecular hydrogen bonding can significantly boost the intermolecular interactions. The resulting membranes exhibited fast solvent permeance and high rejection of dyes not only in water, but also in organic solvents. In addition, the membrane demonstrated excellent performance in precise molecular sieving in organic solvents. This work opens an avenue to designing and fabricating free-standing membranes composed of porous organic materials for efficient molecular sieving.

Crystalline Porous Organic Cage Membranes Constructed Using Fortified Intermolecular Interactions for Molecular Sieving

AbstractAmong the various types of materials with intrinsic porosity, porous organic cages (POCs) are distinctive as discrete molecules that possess intrinsic cavities and extrinsic channels capable of facilitating molecular sieving. However, the fabrication of POC membranes remains highly challenging due to the weak noncovalent intermolecular interactions and most reported POCs are powders. In this study, we constructed crystalline free‐standing porous organic cage membranes by fortifying intermolecular interactions through the induction of intramolecular hydrogen bonds, which was confirmed by single‐crystal X‐ray analysis. To elucidate the driving forces behind, a series of terephthaldehyde building blocks containing different substitutions were reacted with flexible triamine under different conditions via interfacial polymerization (IP). Furthermore, density functional theory (DFT) calculations suggest that intramolecular hydrogen bonding can significantly boost the intermolecular interactions. The resulting membranes exhibited fast solvent permeance and high rejection of dyes not only in water, but also in organic solvents. In addition, the membrane demonstrated excellent performance in precise molecular sieving in organic solvents. This work opens an avenue to designing and fabricating free‐standing membranes composed of porous organic materials for efficient molecular sieving.

The conformational properties of alamethicin in ethanol studied by NMR.

Alamethicin, a peptide consisted of 20 amino acid residues, has been known to function as an antibiotic. The peptides self-associate in biological membranes, form an ion channel, and then induce cell death by leaking intracellular contents through a transmembrane pore of an ion channel. We investigated conformation and its thermal stability of alamethicin-A6 and -U6 in ethanol using proton nuclear magnetic resonance (NMR) spectroscopy; alamethicin-A6 and -U6 have the amino acid sequences of UPUAUAQUVUGLUPVUUQQO and UPUAUUQUVUGLUPVUUQQO, respectively, where U and O represent α-aminoisobutyric acid and phenylalaninol, respectively. As indicated by the under bars in the sequences, only the residue 6 differs between the alamethicins. We show that the alamethicins in ethanol form helix conformation in the region of the residues 2-11 and a non-regular conformation in the regions of the N- and C-termini, and that the helices are maintained up to 66°C at least. Conformations in the region of the residues 12-18 of the alamethicins, however, are not well identified due to the lack of NMR data. In addition, we demonstrate that the amide proton chemical shift temperature coefficients' method, which is known as an indicator for intramolecular hydrogen bonds in peptides and proteins in aqueous solutions, can be also applied to the alamethicins in ethanol. Further, we show that the conformation around the C-terminus of alamethicin-A6 is restrained by intramolecular hydrogen bonds, whereas that of alamethicin-U6 is either restrained or unrestrained by intramolecular hydrogen bonds; the alamethicin-U6 molecules having the restrained and unrestrained conformations coexist in ethanol. We discuss the two types of conformations using a model chain consisting of particles linked by rigid bonds called as the free jointed chain.

Theoretical study on the effect of different positions of -CN group on photophysical properties and forward-reverse ESIPT behaviours of 2,5-bis(benzo[d]thiazol-2-yl)phenol derivatives

Excited state intramolecular proton transfer (ESIPT) compounds have been widely used in many fields due to its unique photophysical properties, but they are strongly affected by substituents. There are many studies on the effect of substituents at the same position on the ESIPT process, but there are few studies on the effects of substituents at different positions on the proton transfer process. In this work, a strong electron-withdrawing cyano group ( – CN) was introduced into different positions of 2,5-bis(benzo[d]thiazol-2-yl)phenol. The effect of different substituted positions on intramolecular hydrogen bond (IHB), photophysical properties and forward-reverse energy barrier of ESIPT reaction have been systematically investigated adopting density functional theory (DFT) and time-dependent DFT. The result showed that the introduction of – CN group at different positions led to a slight red-shift of absorption, and intramolecular charger transfer is the intrinsic reason for this photophysical phenomenon. The position of – CN group obviously influenced the excited state IHB, and then had an effect on ESIPT process. The substitution positions in the left benzo[d]thiazole ring and phenol ring respectively hinder and promote the ESIPT process, while the substitution in the right benzo[d]thiazole ring not only impetus the ESIPT process, but also increase the tautomer fluorescence.

Biological evaluation of a novel Schiff base ligand as an antioxidant agent: Synthesis, characterization and DFT computations of its Ni(II) and Cu(II) complexes

By condensation reaction in methanolic medium, a novel ligand using methoxy substituted amine and 5-bromosalicylaldehydic was synthesized. Then, its Cu- and Ni- complexes were also prepared under same experimental conditions. The final desired compounds, with high obtained yields, have been characterized and well discussed by EA-CHN, UV–Vis., FT-IR, NMR, SEM-EDX and MS spectrometry. The structure of the ligand was confirmed by X-ray crystallography showing an interesting intramolecular hydrogen bond and also intermolecular interactions (Br…CArom. and CH/π-type). The electronic properties were quantified by density functional theory (DFT) calculations using DFT- B3LYP/6-31 G (d,p) level basis set. The molecular structures, geometrical parameters, chemical reactivity, stability, molecular electrostatic potential (MEP) and Mulliken atomic charges were computed to identify the chemical reactive sites on the molecular surface. The antioxidant activities were studied theoretically involving various parameters such as bond dissociation enthalpy (BDE), ionization potentials (IPs), proton affinities (PA), proton dissociation enthalpy (PDE), electron transfer enthalpy (ETE) and radical stabilization energy (RSE). Experimentally, the antioxidant activities were also studied by using 2,2′-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), ferric ion reducing antioxidant power (FRAP) and nitric oxide scavenging (SNP) methods. The computational study of antioxidant activity is well correlated with their experimental results.

Very Strong Hydrogen Bond in Nitrophthalic Cocrystals.

This work presents the studies of a very strong hydrogen bond (VSHB) in biologically active phthalic acids. Research on VSHB comes topical due to its participation in many biological processes. The studies cover the modelling of intermolecular interactions and phthalic acids with 2,4,6-collidine and N,N-dimethyl-4-pyridinamine complexes with aim to obtain a VSHB. The four synthesized complexes were studied by experimental X-ray, IR, and Raman methods, as well as theoretical Car-Parrinello Molecular Dynamics (CP-MD) and Density Functional Theory (DFT) simulations. By variation of the steric repulsion and basicity of the complex' components, a very short intramolecular hydrogen bond was achieved. The potential energy curves calculated by the DFT method were characterized by a low barrier (0.7 and 0.9 kcal/mol) on proton transfer in the OHN intermolecular hydrogen bond for 3-nitrophthalic acid with either 2,4,6-collidine or N,N-dimethyl-4-pyridinamine cocrystals. Moreover, the CP-MD simulations exposed very strong bridging proton dynamics in the intermolecular hydrogen bonds. The accomplished crystallographic and spectroscopic studies indicate that the OHO intramolecular hydrogen bond in 4-nitrophthalic cocrystals is VSHB. The influence of a strong steric effect on the geometry of the studied cocrystals and the stretching vibration bands of the carboxyl and carboxylate groups was elaborated.

Solvent polarity dependent photo-induced excited state intramolecular proton transfer for triphenylamine centered bis unsymmetrical azine (TPOV): A computational study

The exquisite, regulated characteristics of triphenylamine (TPA) derivatives have served as a profound inspiration in the photochemical field. Herein, the novel TPA-centered bis unsymmetrical azine (i.e., 3-methoxysalicylaldehyde substituted 4-((E)-hydrazonomethyl)-N-(4-((E)-hydrazonomethyl)phenyl)-N-phenylaniline (TPOV)) is investigated regarding its photo-induced behaviors and excited state intramolecular proton transfer (ESIPT) mechanisms. Solvent polar-dependent hydrogen bonding interactions and charge recombination, which is induced by photoexcitation, can greatly promote the ESIPT reactions of the TPOV chemosensor. In order to unveil the detailed excited state reaction mechanism, we theoretically construct the S0-state and S1-state of potential energy surfaces (PESs). Based on the S1-state PESs for TPOV in toluene, chloroform, and acetonitrile solvents, we unveil the single ESIPT reaction of TPOV that happens along with alternative dual intramolecular hydrogen bonds (O1-H2···N3 and O4-H5···N6). The solvent polarity-regulated excited state might clear the path for the creation of innovative luminescent materials.

The effect of a novel MOF containing benzophenone structure on the crystallization and ultraviolet protection capacity of PA5,6

In order to improve the UV protection efficiency of conventional Metal organic Framework (MOF), the introduction of benzophenone in MOF was chosen. In this work, with the assistance of 4,4 ' -bipyridine, 3,3′,4,4′-benzophenonetetracarboxylic acid (BPTC) was added to make benzophenone derivatives as organic ligands to coordinate with Cu2+ to form a new MOF ( [ Cu2 ( BPTC) ( bpy) 2]), which was named as CuBb. Then, CuBb are added into PA5,6 to prepare PA5,6/CuBb composites. It was shown that CuBb can improve the crystallization of PA5,6 by promoting the intramolecular hydrogen bonds of PA5,6 under the action of MOF. Also, PA5,6 has low UV transmittance and possesses good UV resistance (ultraviolet protection factor (UPF) exceeds 30) after the addition of CuBb. CuBb is good nucleating agent and UV-resistance agent for PA5,6.

Strengthening an Intramolecular Non-Classical Hydrogen Bond to Get in Shape for Binding.

In this research article, we report on the strengthening of a non-classical hydrogen bond (C-H⋅⋅⋅O) by introducing electron withdrawing groups at the carbon atom. The approach is demonstrated on the example of derivatives of the physiological E-selectin ligand sialyl Lewisx (1, sLex). Its affinity is mainly due to a beneficial entropy term, which is predominantly caused by the pre-organization of sLex in its binding conformation. We have shown, that among the elements responsible for the pre-organization, the stabilization by a non-classical hydrogen bond between the H-C5 of l-fucose and the ring oxygen O5 of the neighboring d-galactose moiety is essential and yields 7.4 kJ mol-1. This effect could be further strengthened by replacing l-fucose by 6,6,6-trifluoro-l-fucose leading to an improved non-classical H-bond of 14.9 kJ mol-1, i.e., an improved pre-organization in the bioactive conformation. For a series of glycomimetics of sLex (1), this outcome could be confirmed by high field NMR-shifts of the H-C5Fuc, by X-ray diffraction analysis of glycomimetics co-crystallized with E-selectin as well as by isothermal titration calorimetry. Furthermore, the electron-withdrawing character of the CF3-group beneficially influences the pharmacokinetic properties of sLex mimetics. Thus, acid-stability, a prerequisite for gastrointestinal stability, could be substantially improved.

Structure and Properties of Thermally Stabilized and Ecologically Friendly Organic Cotton Fibers as a New Activated Carbon Fiber Precursor

Organic cotton precursor yarn was impregnated in an aqueous solution consisting of diammonium hydrogen phosphate (DAP), boric acid (BA), and urea (U) mixtures before the thermal stabilization stage and then subjected to heat treatments in an air environment at 245 °C. The effect of chemical pretreatment on organic cotton yarn was examined using methods such as X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and infrared (IR) spectroscopy. The XRD analysis revealed a gradual decrease in the crystalline structure, attributed to the disruption of intermolecular hydrogen bonds. DSC and TGA measurements showed an improved thermal stability due to the formation of pre-graphitic structures with aromatic entities at higher temperatures. For samples chemically impregnated and then stabilized, the char yield values increased from 25% to 68% at 500 °C and 23% to 53% at 1000 °C. Analysis of IR spectra indicated a gradual reduction in both intermolecular and intramolecular hydrogen bonds associated with dehydration and dehydrogenation reactions. The IR spectra also confirmed a decrease in crystallinity with increasing oxidation time, which is consistent with the findings from X-ray diffraction. In addition, the IR spectra showed the presence of C = C bonds, indicating the formation of a crosslinked ladder-like structure. The results showed that DAP-BA-U integration increased the thermal stability of organic cotton fibers and the obtained samples were ready for the next stage, carbonization.Graphical

Effect of number of intramolecular double bonds on photophysical properties and ESIPT processes for Cha-NH2 and its derivatives: A theoretical study

In recent years, the research on excited-state intramolecular proton transfer (ESIPT) reactions has aroused increasingly attention theoretically and experimentally. For a deep exploration, we designed three derivatives of Cha-NH2 with different numbers of carbon–carbon double bonds: Cha-NH2-1, Cha-NH2-2, and Cha-NH2-3. Using density functional theory and time-dependent density functional theory methods, we systematically studied the photophysical properties and ESIPT processes of Cha-NH2 and its derivatives. Detailed analysis revealed that the number of carbon–carbon double bonds within the molecule has a significant impact on the ESIPT behavior and spectral properties of Cha-NH2 and its derivatives. Specifically, as the number of carbon–carbon double bonds increases, the strength of intramolecular hydrogen bond is gradually weakened, leading to a red shift in the spectrum and a increase in the forward energy barrier for ESIPT, which is unfavorable for the occurrence of the ESIPT reaction. Therefore, this finding opens up broad application prospects for the adjustment and optimization of future ESIPT process.

Bis(Dicarbollide) Complexes of Transition Metals: How Substituents in Dicarbollide Ligands Affect the Geometry and Properties of the Complexes.

The interaction between different types of substituents in dicarbollide ligands and their influence on the stabilization of various rotational conformers (rotamers) of transition metal bis(dicarbollide) complexes [3,3'-M(1,2-C2B9H11)2]- are considered. It has been shown that the formation of intramolecular CH···X hydrogen bonds between dicarbollide ligands is determined by the size of the proton acceptor atom X rather than its electronegativity. Due to the stabilization of rotamers with different dipole moments, intramolecular hydrogen bonds between ligands in transition metal bis(dicarbollide) complexes can have a significant impact on the biological properties of their derivatives. In the presence of external complexing metals, weak intramolecular CH···X hydrogen bonds can be broken to form stronger X->M donor-acceptor bonds. This process is accompanied by the mutual rotation of dicarbollide ligands and can be used in sensors and molecular switches based on transition metal bis(dicarbollide) complexes.

Characterizing the Dynamics of Solvated Disaccharides with In-Electrospray Ionization Hydrogen/Deuterium Exchange-Mass Spectrometry.

Carbohydrates have various biological functions that are based on their structures. However, the composition and the glycosidic-bond linkage and configuration of carbohydrates present challenges for their characterization. Furthermore, isomeric features contribute to the formation of intramolecular hydrogen bonds, which influence the flexibility and dynamics of carbohydrates. Hydrogen/deuterium exchange-mass spectrometry (HDX-MS) enables the analysis of protein dynamics by monitoring deuterium labeling after HDX for different lengths of time. In-electrospray ionization (in-ESI) HDX-MS has been used to rapidly label solvated carbohydrates with labeling occurring during desolvation of ESI droplets. Therefore, HDX-labeling times can be altered by changing the spray-solvent conductivity, which changes the initial size of ESI droplets and their resulting lifetimes. Here, we utilize in-ESI HDX-MS to characterize nine isomeric disaccharides with different monosaccharide compositions and glycosidic-bond linkages and configurations. We compared both the relative D-uptake of isomers at individual conductivities, or HDX-labeling times, and the trends associated with labeling at multiple conductivities. Interestingly, the relative D-uptake trends were correlated to isomeric features that affect disaccharide flexibility, including formation of intramolecular hydrogen bonds. Among the isomeric features studied, linkage was observed to have a significant influence on relative D-uptake with (1-3)-linked disaccharides having more change in relative D-uptake with changing conductivity compared to other linkages. Overall, this research illustrates how in-ESI HDX-MS can be applied to structurally characterize disaccharides with distinct isomeric features. Furthermore, this work shows that in-ESI HDX-MS can be used to monitor the dynamics of solvated molecules with rapidly exchanging functional groups.

Rotational Spectroscopy as a Tool to Characterize Sweet Taste: The Study of Dulcin.

According to old theories of sweetness, the perception of sweet substances is closely linked to the arrangement of atoms within them. To assess the validity of these theories, we conducted an analysis of the structure of the artificial sweetener dulcin for the first time, utilizing microwave spectroscopy and a laser ablation source. These techniques have enabled the identification of two conformers, which are stabilized by an intramolecular hydrogen bond between the amino group and the phenyl ring. The observed conformations were examined in light of the Shallenberger-Acree-Kier molecular theory of sweet taste, and they align with the hypothesized criteria. Furthermore, the study illustrates how conformational relaxation can alter the equilibrium conformational distribution, resulting in the absence of certain conformers in the conformational landscape.

Crystal structure of Staudtienic acid, a diterpenoid from Staudtia kamerunensis Warb. (Myristicaceae).

This title compound, C20H26O2, was isolated from the benzene fraction of the stem bark of Staudtia kamerunensis Warb. (Myristicaceae) using column chromatography techniques over silica gel. The compound was fully characterized by single-crystal X-ray diffraction, one and two-dimensional NMR spectroscopy, IR and MS spectrometry. The compound has two fused cyclo-hexane rings attached to a benzene ring, with a carb-oxy-lic acid on C-4. This cyclo-hexene ring has a chair conformation while the other adopts a half-chair conformation. The benzene ring is substituted with a propenyl moiety. The structure is characterized by inter-molecular O-H⋯O hydrogen bonds, two C-H⋯O intra-molecular hydrogen bonds and two C-H⋯π inter-actions. The mol-ecular structure confirms previous studies carried out by spectroscopic techniques.