threo-Diethyl 2-ethyl-2-hy­droxy-3-(4-methyl­benzene­sulfonamido)­succinate

Sofiane Mekki; Valérie Rolland; Arie van Lee; Marc Rolland

doi:10.1107/S1600536811029527

. 2011 Jul 30;67(Pt 8):o2181–o2182. doi: 10.1107/S1600536811029527

threo-Diethyl 2-ethyl-2-hydroxy-3-(4-methylbenzenesulfonamido)succinate

Sofiane Mekki ^a, Valérie Rolland ^b, Arie van Lee ^c,^*, Marc Rolland ^c

PMCID: PMC3257162 PMID: 22247718

Abstract

The asymmetric unit of the title compound, C₁₇H₂₅NO₇S, contains two independent molecules, which are enantiomers forming a hydrogen-bonded dimer associated with two R ₂ ²(7) patterns. In each molecule, one ethyl group from the two available ethyl ester functional groups is disordered. In one molecule, the ethyl group of the ester function from an α-carboxylic acid is positionally disordered over two sets of sites with occupancies of 0.66:0.34. In the second molecule, it is the ethyl group in the γ-ester function that is disordered over two sets of sites with occupancies of 0.58:0.42.

Related literature

For our studies on optically pure β-substituted β-hydroxy aspartates as glutamate transporter blockers, see: Wehbe et al. (2003a ▶,b ▶,c ▶); Mekki et al. (2011a ▶,b ▶). For hydrogen-bond motifs, see: Etter (1990 ▶); Bernstein et al. (1995 ▶). For the visualization of non-covalent interactions, see: Johnson et al. (2010 ▶); Jmol (2011) ▶. For a description of the Jmol toolkit for the preparation of enhanced figures, see: McMahon & Hanson (2008 ▶).

Experimental

Crystal data

C₁₇H₂₅NO₇S
M _r = 387.44
Triclinic,
a = 9.5424 (3) Å
b = 12.2708 (4) Å
c = 18.2427 (5) Å
α = 90.800 (2)°
β = 91.153 (2)°
γ = 112.513 (3)°
V = 1972.36 (10) Å³
Z = 4
Cu Kα radiation
μ = 1.79 mm⁻¹
T = 173 K
0.27 × 0.24 × 0.12 mm

Data collection

Agilent Xcalibur Sapphire3 Gemini diffractometer
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2010 ▶) T _min = 0.110, T _max = 1.000
25194 measured reflections
6999 independent reflections
6214 reflections with I > 2σ(I)
R _int = 0.043

Refinement

R[F ² > 2σ(F ²)] = 0.040
wR(F ²) = 0.114
S = 1.02
6999 reflections
527 parameters
81 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.34 e Å⁻³
Δρ_min = −0.31 e Å⁻³

Data collection: CrysAlis PRO (Agilent, 2010 ▶); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97; molecular graphics: OLEX2 (Dolomanov et al., 2009 ▶) and Jmol (Jmol, 2011 ▶); software used to prepare material for publication: PLATON (Spek, 2009 ▶) and publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811029527/dn2708sup1.cif

e-67-o2181-sup1.cif^{(41.4KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811029527/dn2708Isup2.hkl

e-67-o2181-Isup2.hkl^{(342.5KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536811029527/dn2708Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Enhanced figure: interactive version of Fig. 4

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N11—H11⋯O32	0.84 (2)	2.23 (2)	3.0426 (18)	162 (2)
O31—H31⋯O22	0.80 (2)	2.10 (2)	2.7747 (17)	142 (2)
N12—H12⋯O31	0.86 (2)	2.19 (2)	3.019 (2)	161 (2)
O32—H32⋯O21	0.81 (2)	2.15 (2)	2.8321 (17)	142 (2)

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Acknowledgments

This work was supported by the Erasmus Mundus Averroés program.

supplementary crystallographic information

Comment

In the present work, as a part of an on-going study of asymmetric syntheses of optically pure β-substituted β-hydroxy aspartates (Wehbe et al., 2003a,b,c; Mekki et al., 2011a,b), the structure of a new compound, threo-diethyl 2-ethyl-2-hydroxy-3-(4-methylphenylsulfonamido)succinate, is described. The key step of the synthesis is the regiospecific Sharpless aminohydroxylation on an ethyl fumarate derivative.

The crystal structure is made up by racemic dimers formed by two independent homochiral molecules ((2S,3S) and (2R,3R) for (I) and (II), respectively). They are bonded by non-covalent NH···O and OH···O hydrogen bonds (Fig. 1) forming two R²₂(7) patterns (Etter, 1990; Bernstein et al., 1995), where the H···O distances range from 2.10 (2) Å to 2.232 (19) Å and the D—H···O angles from 142 (2) to 161.9 (18) ° (Table 1). In order to get an idea of the relative strength of the NH···O and OH···O hydrogen bonds the intersection of the Van der Waals surfaces of donor hydrogen and acceptor was calculated using the program Jmol (Jmol, 2011; 'contact' command with 'full' and 'hbond' options). The resulting Fig. 2 shows clearly that the Van der Waals interaction zones between the hydroxyl groups and the carbonyl ester O atoms are more important than those between the hydroxyl groups and the secondary amine group. The latter interaction zones are much smaller than the former ones. A calculation based on the electron density and its derivatives (Johnson et al., 2010; calculation done in Jmol using the 'contact' command with 'nci' and 'hbond' as options) gives slightly different results (Fig. 3), in the sense that one of the OH···O interactions appears to be negligible. The relevant Van der Waals surfaces may be inspected in the enhanced Jmol picture in Fig. 4. This pictorial view of the non-covalent interaction regions is not completely in agreement with what could be concluded from the directionality of the interaction which is greater for nitrogen as hydrogen bond donor than for oxygen (Table 1). The dimeric structure bears much similarity with those reported recently for the two concomitant β-benzyl β-hydroxy aspartate analogue polymorphs (Mekki et al., 2011a).

The two independent homochiral molecules are very approximately related by a local inversion center between the two molecules. That this local center is only very approximate, can be clearly seen in Fig. 5, which shows the best superposition of the (2S,3S) molecule (I) and the (2S,3S) inversion center related molecule (II) as calculated with Olex2 (Dolomanov et al., 2009). The root-mean-squared deviation (considering the majority disordered parts only) between the two molecules is 0.780 Å. The main conformational differences between molecules (I) and (II) stem from the orientation of the ethyl ester moiety in both residues. This is well illustrated by the torsion angles C9—O5—C4—C3 (-4.2 (2)° and 173.6 (3)° for molecules (I) and (II), respectively) and C1–01-C7—C8 (-165.5 (3)° and -88.6 (2)° for molecules (I) and (II), respectively).

In both molecules, the S1—N1(H1)—C2 pseudo-torsion angle [140.2 (1)° for (I) and -143.3 (1)° for (II)] implies a slight pyramidalization of the sulfonamide moiety.

Experimental

A solution of (0.04 mmole, 14.7 mg) K₂[OsO₂(OH)₄] in water (2.5 ml) and chloramine-T (1.5 mmole, 423 mg) was added to a solution of diethyl 2-ethylfumarate (20 mg, 0.1 mmole) and (DHQD)₂PHAL (0.05 mmole, 39 mg) in CH₃CN (1.25 ml). After 1 h stirring at room temperature a second fraction of diethyl 2-ethylfumarate (180 mg, 0.9 mmole) in CH₃CN (1.25 ml) was added to the reaction mixture. After 5 h, a solution of Na₂SO₃ (357 mg) in water (5.4 ml) was added an the reaction mixture was extracted 3 times with AcOEt (5.4 ml). The fraction was then washed with brine and dried under MgSO₄. The solvent was removed and the title compound was recrystallized in cyclohexane by slow evaporation at ambient temperature yielding colourless crystals in the form of relatively large prisms.