title: Conformational studies of oligomeric oxetane-based dipeptide isosteres derived from L-rhamnose or D-xylose.
abstract: Conformational investigations have been undertaken on oligomers (dimers, tetramers, hexamers) of five closely related oxetane-based dipeptide isosteres. All the oligomers were subjected to a range of studies by NMR, FT-IR and CD spectroscopy. The oligomers derived from methyl 2,4-anhydro-5-azido-3-O-tert-butyldimethylsilyl-5-deoxy-L-rhamnonate 'monomer' all exhibited evidence of ordered conformations in chloroform and 2,2,2-trifluoroethanol (TFE) solution. 5-Acetamido and N-methylamide derivatives of the L-rhamnonate 'monomer', along with a 'dimer' lacking silyl protection at C-3, were synthesized to ascertain the role of intramolecular interactions. This led to the conclusion that, for the L-rhamnonate oligomers, steric interactions govern the conformational preference observed. The equivalent silyl-protected D-lyxonate oligomers gave ordered CD spectra in TFE solution, but NMR and FT-IR spectroscopy in chloroform solution suggested an irregular, non-hydrogen bonded system. The remaining silyl-protected 6-deoxy-L-altronate, 6-deoxy-D-gulonate and D-fuconate oligomers appear to be characterized by their lack of ordered conformation in TFE and chloroform solution.
authors.affiliation: Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK.
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Johnson
authors.forename: Sarah F
authors.initials: SF
authors.lastname: Jenkinson
authors.forename: Ignacio
authors.initials: I
authors.lastname: Pérez-Victoria
authors.forename: Alison A
authors.initials: AA
authors.lastname: Edwards
authors.forename: Timothy D W
authors.initials: TD
authors.lastname: Claridge
authors.forename: George E
authors.initials: GE
authors.lastname: Tranter
authors.forename: George W J
authors.initials: GW
authors.lastname: Fleet
authors.forename: John H
authors.initials: JH
authors.lastname: Jones
mesh_terms: D002942:Circular Dichroism; D004151:Dipeptides / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D011487:Protein Conformation; D012210:Rhamnose / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D014994:Xylose / Q000737:chemistry*
chemical_list: D004151:Dipeptides; D014994:Xylose; D012210:Rhamnose