4-Hydroxy-5-(4-methoxyphenyl)pyrrolidin-2-one

In the title compound, C11H13NO3, the pyrrolidin-2-one ring is in an envelope conformation with the hydroxyl and 4-methoxyphenyl substituents mutually cis. The methoxy group is slighty twisted away from the mean plane of the attached benzene ring. The molecules are arranged into screw chains along the c axis. These chains are interconnected via intermolecular O—H⋯O and N—H⋯O hydrogen bonds into sheets parallel to the ac plane. The crystal structure is further stabilized by weak intermolecular C—H⋯O and C—H⋯π interactions.

In the title compound, C 11 H 13 NO 3 , the pyrrolidin-2-one ring is in an envelope conformation with the hydroxyl and 4methoxyphenyl substituents mutually cis. The methoxy group is slighty twisted away from the mean plane of the attached benzene ring. The molecules are arranged into screw chains along the c axis. These chains are interconnected via intermolecular O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds into sheets parallel to the ac plane. The crystal structure is further stabilized by weak intermolecular C-HÁ Á ÁO and C-HÁ Á Á interactions.

Comment
Many naturally occurring compounds containing a tetramic acid ring system such as radicamine, fuligorobin and codonopsinine possess potent antibiotic, antiviral, antifungal, cytotoxic (Royles, 1996) as well as hypotensive activities (Iida et al., 1986). The title compound, C 11 H 13 NO 3 , can act as an essential intermediate in the synthesis of such tetramic acid derivatives (Chandrasekhar et al., 2006;Gurjar et al., 2006;Yoda et al., 1996), which eventually can be used as a template in multi-step syntheses of biologically active natural products. We have synthesized the title compound (I) and its structure is reported here, Fig. 1.
In (I), the pyrrolidine-2-one ring adopts an envelope conformation with atom C3 displaced from the C1/C2/C3/N1 plane by 0.219 (3) Å, and with puckering parameters (Cremer & Pople, 1975) Q = 0.357 (3) Å and φ = 117.9 (4)°. The bond angles around C1 atom are indicative of sp 2 hybridization. The hydroxyl and 4-methoxyphenyl substituents are attached to the pyrrolidin-2-one ring at atom C3 and C4, respectively and is in cis-configuration (Fig. 1). The methoxy group is slightly twisted away from the mean plane of the phenyl ring as shown by the torsion angle C11-O3-C8-C7 = −5.2 (4)° All bond lengths and angles show normal values (Allen et al., 1987) In the crystal packing of the title compound (Fig. 2), the molecules are arranged into screw chains along the c direction.

Experimental
The synthetic approach to the title compound began with the esterification of p-hydroxyphenylglycine (10.00 g, 60.10 mmol) and thionyl chloride in methanol to give the ester product (10.30 g, 95%). Amine protection (10.00 g, 54.9 mmol) was then carried out using tert-butoxycarbonyl (Boc 2 O) and triethylamine (Et 3 N) in tetrahydrofuran (THF) to give the N-Boc protected product in 85% yield (13.12 g). The hydroxyl functional group (13.01 g, 46.66 mmol) was protected by converting it to the methyl ether using potassium carbonate and methyl iodide (12.72 g, 93%). Condensation between the N-Boc methyl ester (8.30 g, 28.30 mmol) and methyl malonyl chloride in equimolar amounts furnished an intermediate diester (10.60 g, 95%). Dieckmann cyclization of this intermediate diester (5.50 g, 13.99 mmol) with potassium tert-butoxide (t-BuOK) in toluene gave the carbon skeleton β,β diketoester in 45% yield (1.65 g). Demethoxycarbonylation of the β,β diketoester (0.30 g, 1.1 mmol) was successfully carried out by refluxing in 50 ml acetonitrile to give the basic pyrrolidinone ring skeleton (0.23 g, 99%). Reduction of this diketone (0.16 g, 0.77 mmol) was then carried out in sodium borohydride/methanol at 273 K to give the title compound (0.04 g, 24%). Single crystals suitable for X-ray structure determination were obtained by slow evaporation of an ethyl acetate-petroleum ether (2:1 v/v) solution after several days.

sup-2
Refinement H atoms attached to O and N atoms were located in a difference Fourier map and were refined isotropically. H atoms bound to C were placed in calculated positions with d(C-H) = 0.93 Å, U iso =1.2U eq (C) for aromatic 0.98 Å, U iso = 1.2U eq (C) for CH, 0.97 Å, U iso = 1.2U eq (C) for CH 2 , 0.96 Å, U iso = 1.5U eq (C) for CH 3 atoms. A rotating group model was used for the methyl groups. A total of 1121 Friedel pairs were merged before final refinement as there is no large anomalous dispersion for the determination of the absolute configuration. Fig. 1. The molecular structure of (I), showing 40% probability displacement ellipsoids and the atomic numbering.

Special details
Experimental. The data was collected with the Oxford Cyrosystem Cobra low-temperature attachment. 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 > 2sigma(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq O1 0.69354 (13