title: An unexpected tetragonal unit cell for N-(L-2-aminobutyryl)-L-serine.
abstract: The title dipeptide {systematic name: (S)-2-[(S)-2-azaniumylbutanamido]-3-hydroxypropanoate}, C₇H₁₄N₂O₄, was synthesized in the anticipation that it would form nanoporous crystals with hexagonal symmetry. Single-crystal X-ray diffraction analysis showed that it had instead adopted a unit cell in the space group I4, similar to L-alanyl-L-alanine [Fletterick, Tsai & Hughes (1970). J. Phys. Chem. 75, 918-922]. The resulting packing arrangement has a high density for a peptide (1.462 Mg m⁻³), which is rendered possible by extensive disorder over two positions for the ethyl side chain of the 2-aminobutyric acid fragment and over three positions for the serine side chain.
authors.affiliation: Department of Chemistry, University of Oslo, PO Box 1033 Blindern, N-0315 Oslo, Norway.
authors.forename: Carl Henrik
authors.initials: CH
authors.lastname: Görbitz
authors.forename: Vitthal N
authors.initials: VN
authors.lastname: Yadav
mesh_terms: D002087:Butyrates / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004151:Dipeptides / Q000138:chemical synthesis / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D012694:Serine / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: D002087:Butyrates; D004151:Dipeptides; D012694:Serine
keywords: crystal structure; dipeptides; disorder