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Cyclo‐β‐peptides: Structure and tubular stacking of cyclic tetramers of 3‐aminobutanoic acid as determined from powder diffraction data
Author(s) -
Seebach Dieter,
Matthews Jennifer L.,
Meden Anton,
Wessels Thomas,
Baerlocher Christian,
McCusker Lynne B.
Publication year - 1997
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19970800116
Subject(s) - chemistry , tetramer , stacking , crystallography , molecule , diffraction , powder diffraction , cyclic peptide , x ray crystallography , crystal structure , stereochemistry , peptide , organic chemistry , enzyme , biochemistry , physics , optics
The solid‐state structures of three stereoisomer, 1–3 , of the cyclic tetramer of 3‐aminobutanoic acid are presented. These cyclo‐β‐peptides were found to be highly insoluble materials, and it proved to be impossible to grow crystals of sufficient quality for X‐ray single‐crystal analysis. The samples of 1–3 were, however, suitable candidates for structure determination from powder diffraction data ( Fig. 1 ), and the application of this method is described. All three isomers have been found to adopt tubular structures ( Figs. 2–4 ) in a fashion similar to those already observed for certain cyclo‐α‐peptides. The stacks of 16‐membered rings are held together by four nonlinear CO…HN H‐bonds between pairs of molecules ( Fig.5 ).