Phloretin [2’,4’,6’-trihydroxy-3-(4-hydroxyphenyl)-propiophenone] is a polyphenolic known by its anti-oxidant activity and it is mainly found in apples. Besides its potential antioxidant property, the anti-allergic, anti-inflammatory, antimicrobial and anti-cancer activity of phloretin have attracted the attention of food manufacturers and consumers [1] [2] [3] [4]. Meanwhile, the benefits of phloridzin or other phloretin derivatives for human health are well documented by a number of publications and patents. Most of these relate to diabetes, obesity, stress hyperglycemia, membrane permeability and longevity-extending agents in foods, beverages, food additives, pharmaceuticals and cosmetics [5] - [10]. In order to be in compassion with the phloretin, two acetylation products of phloretin(2-(3-(4-acetoxyphenyl)propanoyl)benzene-1,3,5-triyl triacetate (1), C₂₅H₂₂O₉ and 4-(3-(4-acetoxyphenyl)propanoyl)-5-hydroxy-1,3-phenylene diacetate (2), C₂₁H₂₀O₈, cf. Scheme 1, Figure 1 and Figure 2) were synthesized and recrystallized from dichloromethane that are suitable for x-ray diffraction.

In (1), the molecule, which contains two intramolecular O···O interactions, is existed as dimer. Each of the molecules exhibits a strong intramolecular interaction of O···O type (Figure 3), the distances O7/O4 and O16/O13 being 2.875 and 2.822 Å, respectively. The intramolecular hydrogen bonds provides two distorted envelop R₁₁(5) rings, O7 and O16 as flap folded upward the mean plane of 0.909 Å and 0.847 Å. This presumably sets the stage for the interactions observed within the crystal lattice. The crystallographic data are presented in Table 1.

The molecules of (1) are linked into sheets by a combination of the types Caryl-H···O, C_sp³-H···O and C_sp³-H···π hydrogen bonds. Although there are many O atoms in the molecule of (1) potentially available as hydrogen-bond acceptors, not at all O atoms in fact play part in the hydrogen bond. Instead, atom O14 acts as a triple acceptor of hydrogen bonds, and atoms O7 and O16 act as a double acceptor of hydrogen bonds.

In (1), unconventional benzene ring-carbonyl C8-H8···O9ⁱ hydrogen bonding favors the formation of one-dimensional chains, the axes of which run parallel to [100]. Similar one-dimensional chains are observed in the crystal structure of 1,4-phenylenediammonium bis(hydrogen phthalate) [11]. Molecules in adjacent chains (along a axis) are held together by weak types Caryl-H···O, C_sp³-H···O and C_sp³-H···π interactions to form supramolecular. Molecules are arranged in zigzag chains along the c axis and are held together by weak C_sp³-H···O hydrogen bonds between atom H8A of the methoxy group and the carbonyl O atom of a neighbouring molecule.

The molecules of compound 2 exist in O-H···O and C-H···O hydrogen bonds (Table 2), by which molecules are linked into three-dimensional framework structures. The dihedral angle between two benzene rings is 67.15˚. But in (1) the dihedral angle (77.25˚ and 47.27˚ respectively) between two benzene rings in one molecule is strikingly different from the other. The torsion angles of C5-O4-C9-O3 are 5.7(3)˚ (Table 3). Two intermolecular hydrogen bonds C1-H1C···O5ⁱ and C4-H4···O6ⁱ [symmetry codes: (i) x-1, y, z] which connect the molecule in adjacent unit cells to form infinite long chains along the b-axis are observed (cf. Figure 4). Carbonyl C11=O6 is almost planar with the mean of benzene ring from C3 to C8, the maximum deviations from the mean plane through the non-H atoms are 0.094 A˚ for atom O6. While in the crystal of dimer (1) carbonyl C13=O7 is obviously unplanar with the mean of benzene ring from C3 to C8 in one molecular, so is the other molecular (Table 4). The deviations from the mean plane (C3-C8) through the non-H atoms which are 0.955 A˚ for atom O7 and from the mean plane (C26-C31) through the non-H atoms which are 0.812 A˚ for atom O16 are by far larger than 0.094 A˚ in (2).

There are also some important differences in the crystal packing of compound 1 (cf. Figure 5). The molecules 1 is abundant with the good hydrogen bond acceptors

and the good hydrogen bond donor- C=O group-form many hydrogen bonds and contacts. The crystal packing is mostly caused by the interplay of van der Waals, stacking and weak hydrogen bonding interactions. The crystal packing of compound 2 (cf. Figure 6) shows that the molecules connect each other by means of C-H···O hydrogen bonds. These chains are then connected by weaker contacts (C-H···O) into three-dimensional crystal structure.

Diffraction data for I and II were collected at room temperature by the ω-scan technique on an Agilent Technologies Xcalibur four-circle diffractometer with Bruker SMART CCD Eos CCD-detector and graphite-monochromatized MoKa

radiation source (k = 0.71073 A˚). The data were corrected for Lorentz-polarization as well as for absorption effects. The calculations were mainly per-formed within the WinGX program system [12]. The structure was solved with SIR92 [13] and refined with the full-matrix least-squares procedure on F² by SHELXL97 [14]. The scattering factors incorporated in SHELXL97 were used. The function S(|F_o|² − |F_c|²)² was minimized, with w − 1 = [δ²(F_o)² + (A·P)² + B·P](P = [Max(F_o², 0) + 2F_c²]/3. All non-hydrogen atoms were refined anisotropically, the hydrogen atoms were placed geometrically in idealized positions and refined as rigid groups with their Uiso’s as 1.2 times Ueq of the appropriate carrier atom. Relevant crystal data are listed in Table 1, together with refinement details. Crystallographic data (excluding structure factors) for the structural analysis has been deposited with the Cam-bridge Crystallographic Data Centre, Nos. CCDC-1432985 (1), and CCDC-1432986 (2). Copies of this information may be obtained free of charge from: The Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK. Fax:?44(1223)336-033, e-mail: deposit@ccdc.cam.ac.uk, or website: http://www.ccdc.cam.ac.uk/.

In this paper, we synthesized and recrystallized two acetylation product of phloretin(2-(3-(4-acetoxyphenyl)propanoyl)benzene-1,3,5-triyl triacetate (1), C₂₅H₂₂O₉ and 4-(3-(4-acetoxyphenyl)propanoyl)-5-hydroxy-1,3-phenylene diacetate (2), C₂₁H₂₀O₈ that were suitable for x-ray diffraction. Their structures all reveal three-dimensional framework structures, which contain intramolecular O···O interactions, C-H···O, C-H···π(arene) and O-H···O hydrogen bonds, several weak C-H···O interactions of the types Caryl-H···O, C_sp³-H···O, and give cyclic R²₂(9) and R²₂(4) motif. These hydrogen bonds and interactions appear to play an important role in controlling the molecular conformation and activity.

The author is appreciative to Li Wang for the synthesis and analytical support and animal facilities, and also is indebted with Li Wang.

This study was supported in part by grants from Science and Technology Innovation Team Project of Xi’an Medical University, China (2021TD14) and Industrialization Project of Shaanxi Provincial Department of Education, China (20JC031).

The authors have no conflicting interests to declare.

Wang, L. and Xu, R. (2022) Supramolecular Architectures of 2-(3-(4-acetoxyphenyl)propanoyl)benzene-1,3,5-triyl triacetate (1) and 4-(3-(4-acetoxyphenyl)propanoyl)-5-hydroxy-1,3-phenylene diacetate (2). International Journal of Organic Chemistry, 12, 200-207. https://doi.org/10.4236/ijoc.2022.124017