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Figure 9
Topological presentation of the close packing of cis-alicyclic β-amino acids (a) and the results of the type of rotation 8 → 9 in one (b) and two dimensions (c). Since β-amino acids are zwitterions, their symbolic presentation denotes the NH3+ group with a small triangle rotated through 180° to that of NH2 groups in carboxamides, depicted in Fig. 3[link](b), while the COO− moiety is denoted by two small circles. The molecules forming helices are linked by two NH⋯O hydrogen bonds along the twofold screw axes. They enclose symmetry-free R22(8) dimers. The enantiomeric helices are cross-linked by the third N—H⋯O hydrogen bond, simultaneously enclosing the R44(12) and R42(8) tetramers.

Journal logoSTRUCTURAL SCIENCE
CRYSTAL ENGINEERING
MATERIALS
ISSN: 2052-5206
Volume 61| Part 5| September 2005| Pages 536-547
doi:10.1107/S0108768105023189
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