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Antiparallel β‐Sheet Conformation in Cyclopeptides Containing a Pseudo‐amino Acid with a biphenyl moiety
Author(s) -
Brandmeier Volker,
Sauer Wolfgang H. B.,
Feigel Martin
Publication year - 1994
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.19940770110
Subject(s) - chemistry , diastereomer , antiparallel (mathematics) , biphenyl , stereochemistry , atropisomer , moiety , chirality (physics) , amino acid , organic chemistry , biochemistry , physics , nambu–jona lasinio model , chiral symmetry breaking , quantum mechanics , magnetic field , quark
The biphenyl‐containing pseudo‐amino acids 2′‐(aminomethyl)biphenyl‐2‐carboxylic acid (Abc; 1 ) and 2′‐(aminomethyl)biphenyl‐2‐acetic acid (Aba; 2 ) are used as rigid spacers in the backbone of the cyclic peptides cyclo (‐Abc‐Ala‐Phe‐Gly‐) 2 ( 5 ), cyclo(‐Abc‐Ala‐Val‐Gly‐) 2 ( 6 ), cyclo(‐Aba‐Gly‐Phe‐Ala‐) 2 ( 7 ), and cyclo(‐Aba‐Ala‐Phe‐Gly‐) 2 ( 8 ). Three different interconverting diastereoisomers are found in solutions of each of these cyclopeptides due to the atropisomerism of the biphenyl units. NMR Techniques and molecular‐dynamics calculations allow to conclude that the major diastereoisomer of 5 (and 6 ) in (D 6 )DMSO adopts a β‐sheet conformation. It is proposed that the pseudo‐amino acid 1 of ( R )‐chirality forms, with attached L ‐amino acids, a H‐bonding pattern comparable to a β‐turn (see D in Fig. 4 and F ).