(4R)-Ethyl 4-(4-chlorophenyl)-2-hydroxy-5-oxo-2,3,4,5-tetrahydropyrano[3,2-c]chromene-2-carboxylate. Corrigendum

Corrigendum to Acta Cryst. (2010), E66, o217.

The absolute configuration in the title of the paper by Wang, Zhang, Xu & Zhang [Acta Cryst. (2010), E66, o217] is corrected.
The title compound, C 21 H 17 ClO 6 , is optically pure and adopts an R configuration. It was obtained by an organocatalytic asymmetric Michael addition of 4-hydroxycoumarin with (E)ethyl 4-(4-chlorophenyl)-2-oxobut-3-enoate. The structure consists of a tetrahydropyran unit fused to the coumarin ring ring system. The hydroxyl and phenyl groups are on the same side of the tetrahydropyrane ring. The benzene ring is almost perpendicular to the coumarin ring [dihedral angle of 72.89 (3) ]. In the crystal structure, intermolecular O-HÁ Á ÁO hydrogen bonds are observed. An intramolecular O-HÁ Á ÁO contact also occurs.

S1. Comment
Coumarin derivatives are common found in a variety of natural products, and are used as versatile intermediates in organic and natural product synthesis (Fylaktakidou et al., 2004;Hoult et al., 1996). The title compound could be synthesized through an asymmetric Michael addition of 4-hydroxycoumarin with (E)-ethyl 4-(4-chlorophenyl)-2oxobut-3-enoate, catalyzed by a tertiary-amine-squaramide catalyst. As part of our study in organocatalysis, the absolute structure of the title compound was determined, which adopts a R configuration. The structure consists of a tetrahydropyrane fused beside the coumarin ring. The hydroxyl and phenyl groups are on the same side of the tetrahydropyrane ring. The benzene ring is almost perpendicular to the coumarin ring with a dihedral angle of 72.89 (3)° between the mean planes. In addition, intermolecular O-H···O hydrogen bonds are observed in the crystal structure.
The mixture was purified by column chromatography on silica gel, eluted by petroleum ether/EtOAc (10:1 to 3:1) to give the desired Michael adducts. Suitable crystals of the title compound were obtained by slow evaporation of a mixture solution of CH 2 Cl 2 and iPrOH at room temperature.  The asymmetric unit of the structure of the title compound, with the atomic labeling scheme. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
The molecular packing of the title compound showing H-bridge interactions.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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.  (9) 0.0004 (9)  C12 0.0320 (8) 0.0309 (9) 0.0374 (10) −0.0034 (7) 0.0033 (7) −0.0021 (7)  C4 0.0518 (11) 0.0322 (10) 0.0400 (11) −0.0070 (9) 0.0027 (9) 0.0008 (8)