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Redetermined crystal structure of α-dl-me-thio-nine at 340 K.

Görbitz CH, Qi L, Mai NT, Kristiansen H - Acta Crystallogr Sect E Struct Rep Online (2014)

Bottom Line: Bull.Chem.We here present accurate structural data for this polymorph [R(F) = 0.049], which are compared with other related amino acid structures with similar properties.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemistry, University of Oslo, PO Box 1033 Blindern, N-0315 Oslo, Norway.

ABSTRACT
Two forms, α and β, are known for the racemic amino acid dl-me-thio-nine, C5H11NO2S. The phase transition between them, taking place around 326 K, is associated with sliding at the central inter-faces of the hydro-phobic regions in the crystal, leaving the hydrogen-bonding pattern unperturbed. For the high-temperature α phase, only a structure of rather low quality has been available [R factor = 0.118, no H-atom coordinates; Taniguchi et al. (1980 ▶). Bull. Chem. Soc. Jpn, 53, 803-804]. We here present accurate structural data for this polymorph [R(F) = 0.049], which are compared with other related amino acid structures with similar properties. We report for the first time that the side chain of this phase has a minor disorder component [occupancy 0.0491 (18)] with a gauche+ rather than a gauche- conformation for the N-C-C-C group. In the crystal of the title compound, N-H⋯O hydrogen bonds link the mol-ecules into (100) sheets.

No MeSH data available.


Related in: MedlinePlus

The mol­ecular structure of (I), with 50% probability displacement ellipsoids and atomic numbering indicated. The l-enanti­omer was used as the asymmetric unit, d-enanti­omers being generated by symmetry. The minor side-chain orientation [occupancy 0.0491 (18)], with N1—C2B—C3B—C4B in a gauche+ rather than a gauche− orientation (Table 1 ▶), is shown in a lighter colour.
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fig1: The mol­ecular structure of (I), with 50% probability displacement ellipsoids and atomic numbering indicated. The l-enanti­omer was used as the asymmetric unit, d-enanti­omers being generated by symmetry. The minor side-chain orientation [occupancy 0.0491 (18)], with N1—C2B—C3B—C4B in a gauche+ rather than a gauche− orientation (Table 1 ▶), is shown in a lighter colour.

Mentions: The mol­ecular structure of (I) is shown in Fig. 1 ▶. Despite the above-room-temperature conditions, thermal vibrations are comparatively modest. A previously undetected minor conformation with χ1(N1—C2B—C3B—C4B) in a gauche+ orientation (Table 1 ▶) has occupancy 0.0491 (18). If the presence of this rotamer is neglected, the refinement converges at R = 0.0586 rather than 0.0490. Disorder is extensive for all known phases of dl-Abu and dl-Nva, so it is not unexpected that it is observed here for dl-Met.


Redetermined crystal structure of α-dl-me-thio-nine at 340 K.

Görbitz CH, Qi L, Mai NT, Kristiansen H - Acta Crystallogr Sect E Struct Rep Online (2014)

The mol­ecular structure of (I), with 50% probability displacement ellipsoids and atomic numbering indicated. The l-enanti­omer was used as the asymmetric unit, d-enanti­omers being generated by symmetry. The minor side-chain orientation [occupancy 0.0491 (18)], with N1—C2B—C3B—C4B in a gauche+ rather than a gauche− orientation (Table 1 ▶), is shown in a lighter colour.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4257343&req=5

fig1: The mol­ecular structure of (I), with 50% probability displacement ellipsoids and atomic numbering indicated. The l-enanti­omer was used as the asymmetric unit, d-enanti­omers being generated by symmetry. The minor side-chain orientation [occupancy 0.0491 (18)], with N1—C2B—C3B—C4B in a gauche+ rather than a gauche− orientation (Table 1 ▶), is shown in a lighter colour.
Mentions: The mol­ecular structure of (I) is shown in Fig. 1 ▶. Despite the above-room-temperature conditions, thermal vibrations are comparatively modest. A previously undetected minor conformation with χ1(N1—C2B—C3B—C4B) in a gauche+ orientation (Table 1 ▶) has occupancy 0.0491 (18). If the presence of this rotamer is neglected, the refinement converges at R = 0.0586 rather than 0.0490. Disorder is extensive for all known phases of dl-Abu and dl-Nva, so it is not unexpected that it is observed here for dl-Met.

Bottom Line: Bull.Chem.We here present accurate structural data for this polymorph [R(F) = 0.049], which are compared with other related amino acid structures with similar properties.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemistry, University of Oslo, PO Box 1033 Blindern, N-0315 Oslo, Norway.

ABSTRACT
Two forms, α and β, are known for the racemic amino acid dl-me-thio-nine, C5H11NO2S. The phase transition between them, taking place around 326 K, is associated with sliding at the central inter-faces of the hydro-phobic regions in the crystal, leaving the hydrogen-bonding pattern unperturbed. For the high-temperature α phase, only a structure of rather low quality has been available [R factor = 0.118, no H-atom coordinates; Taniguchi et al. (1980 ▶). Bull. Chem. Soc. Jpn, 53, 803-804]. We here present accurate structural data for this polymorph [R(F) = 0.049], which are compared with other related amino acid structures with similar properties. We report for the first time that the side chain of this phase has a minor disorder component [occupancy 0.0491 (18)] with a gauche+ rather than a gauche- conformation for the N-C-C-C group. In the crystal of the title compound, N-H⋯O hydrogen bonds link the mol-ecules into (100) sheets.

No MeSH data available.


Related in: MedlinePlus