3-Hydroxy-2-(4-methoxybenzenesulfonamido)butanoic acid

The title compound, C11H15NO6S, features a distorted tetrahedral geometry for the S atom. One of the sulfonamide O atoms is approximately coplanar with the benzene ring [C—C—S—O torsion angle = −160.81 (7)°], whereas the other lies well below the plane [C—C—S—O = −29.66 (8)°]. In the crystal, O—H⋯O and C—H⋯O hydrogen bonds link the molecules into chains parallel to the b axis.

The title compound, C 11 H 15 NO 6 S, features a distorted tetrahedral geometry for the S atom. One of the sulfonamide O atoms is approximately coplanar with the benzene ring [C-C-S-O torsion angle = À160.81 (7) ], whereas the other lies well below the plane [C-C-S-O = À29. 66 (8) ]. In the crystal, O-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds link the molecules into chains parallel to the b axis.

Comment
The chemistry of sulfonamides is of interest as they show distinct physical, chemical and biological properties. Sulfonamides are used as anticancer, anti-inflammatory and antiviral agents Scozzafava et al., 2003). Amino acid-derived sulfonamides are shown to be active against Procollagen C-terminal protease, which is a member of the metzincin enzyme family Delaet et al., 2003).

Experimental
To a solution of L-threonine (3 mmol, 0.618 g) in distilled water (10 ml), 4-methoxybenzene sulphonyl chloride (3 mmol, 0.357 g) was suspended. The pH of the solution was maintained at 8 by continuously adding 1M sodium carbonate solution throughout the reaction at room temperature. After the completion of the reaction, the pH was adjusted to 2 using 1N HCl solution which resulted in the formation of the precipitate which was filtered, dried and recrystallized in methanol to yield the title compound.

Refinement
Atoms H1N1, H1O5 and H1O6 were located from a difference Fourier map and refined freely [N-H = 0.887 (17)

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
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 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 > 2σ(F 2 ) is used only for calculating Rfactors(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.