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Conformational Study of Heteropentapeptides Containing an α ‐Ethylated α , α ‐Disubstituted Amino Acid: ( S )‐Butylethylglycine (=2‐Amino‐2‐ethylhexanoic Acid) within a Sequence of Dimethylglycine (=2‐Aminoisobutyric Acid) Residues
Author(s) -
Tanaka Masakazu,
Oba Makoto,
Imawaka Naoto,
Tanaka Yoshitsugu,
Kurihara Masaaki,
Suemune Hiroshi
Publication year - 2001
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 - 10.1002/1522-2675(20010131)84:1<32::aid-hlca32>3.0.co;2-4
Subject(s) - chemistry , molecular mechanics , stereochemistry , amino acid , amino acid residue , solid state , sequence (biology) , peptide sequence , crystallography , molecular dynamics , computational chemistry , biochemistry , gene
Heteropentapeptides containing the α ‐ethylated α , α ‐disubstituted amino acid ( S )‐butylethylglycine and four dimethylglycine residues, i.e. , CF 3 CO‐[( S )‐Beg]‐(Aib) 4 ‐OEt ( 4 ) and CF 3 CO‐(Aib) 2 ‐[( S )‐Beg]‐(Aib) 2 ‐OEt ( 7 ), were synthesized by conventional solution methods. In the solid state, the preferred conformation of 4 was shown to be both a right‐handed ( P ) and a left‐handed ( M ) 3 10 ‐helical structure, and that of 7 was a right‐handed ( P ) 3 10 ‐helical structure. IR, CD, and 1 H‐NMR spectra revealed that the dominant conformation of both 4 and 7 in solution was the 3 10 ‐helical structure. These conformations were also supported by molecular‐mechanics calculations.