(1R*,21S*,22R*,24S*)-Methyl ethyl 2-[23-hydroxy-22,24-diphenyl-8,11,14-trioxa-25-azatetracyclo[19.3.1.02,7.015,20]pentacosa-2,4,6,15(20),16,18-hexaen-25-yl]but-2-enedioate

The title compound, C40H41NO8, is a product of the reduction of the cyclic carbonyl group of the γ-piperidone subunit of the aza-14-crown-4 ether with subsequent re-esterification of its dimethyl butenoate substituent into a monoethyl monomethyl group. The azacrown macrocycle exhibits a bowl conformation with a dihedral angle of 70.82 (5)° between the benzene rings fused to it. The piperidine ring adopts a chair conformation and the methyl ethyl ethylenedicarboxylate fragment has a cis conformation, with a dihedral angle of 66.51 (7)° between the two carboxylate groups. The ethyl group is disordered over two sites with occupancies of 0.70 (1):0.30 (1). In the crystal, molecules form inversion dimers, via pairs of O—H⋯O hydrogen bonds, that stack along the a axis.

The title compound, C 40 H 41 NO 8 , is a product of the reduction of the cyclic carbonyl group of the -piperidone subunit of the aza-14-crown-4 ether with subsequent re-esterification of its dimethyl butenoate substituent into a monoethyl monomethyl group. The azacrown macrocycle exhibits a bowl conformation with a dihedral angle of 70.82 (5) between the benzene rings fused to it. The piperidine ring adopts a chair conformation and the methyl ethyl ethylenedicarboxylate fragment has a cis conformation, with a dihedral angle of 66.51 (7) between the two carboxylate groups. The ethyl group is disordered over two sites with occupancies of 0.70 (1):0.30 (1). In the crystal, molecules form inversion dimers, via pairs of O-HÁ Á ÁO hydrogen bonds, that stack along the a axis.
We thank the National Foundation for Science and Technology Development (NAFOSTED) (grant 104.02-2012.44) for financial support of this work. reduce the cyclic carbonyl group of the γ-piperidone subunit into the carbinol one of the initial bis(benzo)-(β,β′-diphenylγ-piperidono)aza-14-crown-4 ether containing N-(dimethyl)maleinate fragment, we found that the expected reduction was accompanied by re-esterification of one methoxy group of the dimethyl butenoate substituent into the ethoxy one (Fig. 1).
The structure of the resulting compound -the higher sterically hindered product (I) was unambiguously established by Xray diffraction analysis.
The title compound I, C 40 H 41 NO 8 , comprises the aza-14-crown-4-ether skeletal moiety and adopts a bowl conformation (Fig. 2). The configuration of the C7-O8-C9-C10-O11-C12-C13-O14-C15 polyether chain is t-g (-) -t-t-g (+) -t (t = trans, 180°; g = gauche, ±60°). The piperidine ring of the bicyclic fragment have a chair conformation. The dihedral angle between the planes of the benzene rings fused to the aza-14-crown-4-ether moiety is 70.82 (5)°. The phenyl rings at the C22 and C24 carbon atoms occupy the sterically favorable equatorial positions, and are rotated to each other by 65.00 (6)°. Contrary to that, the hydroxyl group at the C23 carbon atom occupies the axial position. The methyl ethyl ethylenedicarboxylate fragment has a cis configuration with the dihedral angle of 66.51 (7)° between the two carboxylate groups. The ethyl group is disordered over two sites with the occupancies of 0.70 (1):0.30 (1). The volume of the internal cavity of macrocycle I is approximately equal to 61Å 3 .
The molecule of I possesses four asymmetric centers at the C1, C21, C22 and C24 carbon atoms and can have potentially numerous diastereomers. The crystal of I is racemic and consists of enantiomeric pairs with the following relative configuration of the centers: rac-1R*,21S*,22R*,24S*.

Experimental
A powder of NaBH 4 (1.14 g, 30 mmol) was added to a suspension of azacrown ether (6.47 g, 10 mmol) in ethanol (50 ml). The mixture was stirred for 30 min at r.t. and then boiled for 1 h. After the solvent evaporation, the residue was washed with hot water (30 ml) and purified by re-crystallization from ethanol to give 2.27 g of colourless crystals of I. H, 6.23; N 2.11. Found: C, 72.32; H, 6.19; N, 2.08.
The hydrogen atoms were placed in calculated positions with C-H = 0.95-1.00Å and refined in the riding model with fixed isotropic displacement parameters [U iso (H) = 1.5U eq (C) for the methyl groups and U iso (H) = 1.2U eq (C) for the other groups].

Figure 1
The reaction of reduction and subsequent re-esterification of initial dimethyl 2-[bis(benzo)-(β,β′-diphenyl-γpiperidono)aza-14-crown-4-ether]butenoate.   The projection of the crystal structure of I along the a axis demonstrating the packing of the centrosymmetrical dimers.  Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.