Synthesis and crystal structure of 1,3-bis(acetoxymethyl)-5-{[(4,6-dimethylpyridin-2-yl)amino]methyl}-2,4,6-triethylbenzene

In the crystal structure of the title compound, C26H36N2O4, the tripodal molecule adopts a conformation in which the substituents attached to the central benzene ring are arranged in an alternating order above and below the ring plane.

In the crystal structure of the title compound, C 26 H 36 N 2 O 4 , the tripodal molecule exists in a conformation in which the substituents attached to the central arene ring are arranged in an alternating order above and below the ring plane.The heterocyclic unit is inclined at an angle of 79.6 (1) � with respect to the plane of the benzene ring.In the crystal, the molecules are connected via N-H� � �O bonds, forming infinite supramolecular strands.Interstrand association involves weak C-H� � �O and C-H� � �� interactions, with the pyridine ring acting as an acceptor in the latter case.

Chemical context
Recognition units based on 2-aminopyridine have proved to be valuable building blocks for the construction of artificial carbohydrate receptors that act via non-covalent interactions (Mazik et al., 2004(Mazik et al., , 2005;;Mazik, 2009Mazik, , 2012;;Lippe & Mazik, 2015;Seidel et al., 2023).Such units are able to participate in the formation of hydrogen-bonding motifs similar to those observed in natural complexes for the primary amide groups (side chains of asparagine and glutamine).The latter are used by carbohydrate-binding proteins in combination with other functional groups such as hydroxy, carboxy, imidazolyl and isopropyl groups (side chains of serine, aspartic acid, histidine and valine, respectively).The use of a combination of different functional groups enables not only the formation of neutral and charge-reinforced hydrogen bonds, but also of C-H� � �� interactions and numerous van der Waals contacts, and is responsible for the observed binding selectivities and efficiencies of the proteins (Quiocho, 1989;Sharon & Lis, 2007;Gabius, 2009;Gabius et al., 2011).Our studies with various acyclic and macrocyclic artificial receptors have also shown that selective and effective binding is favourably influenced by the involvement of different functional groups in the binding process.Among the acyclic receptor molecules, 1,3,5-substituted 2,4,6-trialkylbenzene derivatives have been studied particularly intensively (Lippe et al., 2015;Kaiser et al., 2019;Stapf et al., 2020a;Ko ¨hler et al., 2020Ko ¨hler et al., , 2021Ko ¨hler et al., , 2024)), and different binding properties have been observed depending on the nature of the receptor building blocks.In this article, we describe the crystal structure of 1,3-bis(acetoxymethyl)-5-{[(4,6-dimethylpyridin-2-yl)amino]methyl}-2,4,6-triethylbenzene, which is a precursor for the synthesis of a triethylbenzene derivative bearing a 2-aminopyridine-based recognition moiety and two hydroxymethyl groups.

Structural commentary
The crystal structure of the title compound, C 26 H 36 N 2 O 4 , was solved in the monoclinic space group P2 1 /n with the asymmetric unit containing one molecule.As shown in Fig. 1, the molecule adopts a conformation in which the pyridinylamino moiety and the two acetoxy groups are located on one side of the central benzene ring, whereas the ethyl substituents are directed to the opposite side of the ring plane (ababab arrangement; Das & Barbour, 2008a,b, 2009;Koch et al., 2017;Schulze et al., 2017).The molecule exists in a strongly distorted conformation with torsion angles of À 166.6 (1) (anti) and À 121.1).

Database survey
Our previous studies have shown that representatives of 1,3,5substituted 2,4,6-trialkylbenzenes with side arms bearing different functional groups have a better ability to discriminate between various carbohydrate substrates than compounds possessing identical functionalized side arms.In this context, the combination of 2-aminopyridine-based building blocks with other functional groups was shown to provide compounds capable of acting as effective and selective carbohydrate receptors.The search in the Cambridge Structural Database (CSD, Version 5.45, update June 2024; Groom et al., 2016) for such molecules with one or two pyridin-2-ylaminomethyl unit(s) yielded thirteen hits.All crystal structures of the triethylbenzene derivatives listed below have in common that the tripodal molecules adopt a conformation with an alternating arrangement of the substituents above and below the plane of the central benzene ring.Perspective view of the title molecule including atom labelling.Anisotropic displacement ellipsoids are drawn at the 50% probability level.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.The non-hydrogen atoms were refined anisotropically.All hydrogen atoms were positioned

Special details
Geometry.All esds (except the esd in the dihedral angle between two l.s.planes) are estimated using the full covariance matrix.The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry.An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s.planes.

Figure 2
Figure 2 Packing diagram of the title compound.The N-H� � �O hydrogen bonds are shown as dashed lines.

Table 2
Experimental details.