Oxazolidin-2-one-containing pseudopeptides that fold into beta-bend ribbon spirals.
Three sets of oligomers containing the 4-carboxy-5-methyloxazolidin-2-one (Oxd) moiety have been synthesized with the aim of checking whether these molecules are able to fold in ordered structures: A set [Boc-(L-Ala-L-Oxd)(n)-OR], B set [Boc-(L-Ala-D-Oxd)(n)-OR], and C set [Boc-(Aib-L-Oxd)(n)-OR] preferential conformations have been analyzed with IR absorption, NMR, and CD. We have noticed that in these oligomers three stabilizing effects are active: (i) the rigid Oxd -CO-N(CH<)-CO- moiety, which always tend to assume a trans conformation; (ii) the formation of Oxd C=O...H-(alpha)C intramolecolar H-bonds; (iii) the alternate formation of 1 <-- 4 intramolecular C=O...H-N H-bonds. Through the analysis of the experimental data, we could demonstrate that only the oligomers of the B set are able to meet all three requirements listed above. By a deeper insight into the CD spectra, we gathered that the secondary structure adopted by the B set oligomers is a beta-bend ribbon spiral, which is a subtype of the 3(10)-helix.
Tomasini
Claudia
C
Dipartimento di Chimica G. Ciamician, Alma Mater Studiorum Università di Bologna, Via Selmi 2, 40126 Bologna, Italy. claudia.tomasini@unibo.it
Luppi
Gianluigi
G
Monari
Magda
M
D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D009842:Oligopeptides / Q000737:chemistry*; D023303:Oxazolidinones / Q000737:chemistry*; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared
D009842:Oligopeptides; D023303:Oxazolidinones