Helix-forming carbohydrate amino acids.
[reaction: see text] The solution-phase conformational properties of tetrameric and octameric chains of C-glycosyl alpha-d-lyxofuranose configured tetrahydrofuran amino acids (where the C-2 and C-5 substituents on the tetrahydrofuran ring are trans to each other) were examined using NMR and IR and CD in organic solvents. Studies by NMR and IR demonstrated that in chloroform solution, the tetramer 7 does not adopt a hydrogen-bonded conformation whereas the octamer 10 populates a well-defined helical secondary structure stabilized by 16-membered (i, i - 3) interresidue hydrogen bonds, similar to a pi-helix. Circular dichroism studies in trifluoroethanol are consistent with this conformation for the octamer 10, and also indicate that the tetramer 7 adopts a rigid conformation not stabilized by hydrogen bonds.
Claridge
Timothy D W
TD
Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, United Kingdom.
Long
Daniel D
DD
Baker
Christopher M
CM
Odell
Barbara
B
Grant
Guy H
GH
Edwards
Alison A
AA
Tranter
George E
GE
Fleet
George W J
GW
Smith
Martin D
MD
D000596:Amino Acids / Q000737:chemistry*; D002241:Carbohydrates / Q000737:chemistry*; D008956:Models, Chemical; D008968:Molecular Conformation; D011108:Polymers / Q000138:chemical synthesis*; D017433:Protein Structure, Secondary; D013055:Spectrophotometry, Infrared
D000596:Amino Acids; D002241:Carbohydrates; D011108:Polymers