Ilia A. Guzei

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A highly stereoselective synthesis of novel cyclically constrained gamma-amino acid residues is presented. The key step involves organocatalytic Michael addition of an aldehyde to 1-nitrocyclohexene. After aldehyde reduction, this approach provides optically active beta-substituted delta-nitro alcohols (96-99% ee), which can be converted to gamma-amino acid(More)
Foldamers, oligomers with strong folding propensities, are subjects of growing interest because such compounds offer unique scaffolds for the development of molecular function. We report two new foldamer classes, oligopeptides with regular 1:2 or 2:1 patterns of alpha- and beta-amino acid residues. Two distinct helical conformations are detected via 2D NMR(More)
Design of functional foldamers requires knowledge of the conformational propensities of constituent residues. Here, we explore the effects of variations in both alpha-amino acid and beta-amino acid substitution on alpha/beta-peptide helicity. We also report the first X-ray crystal structure of a helical alpha/beta-peptide. We conclude that a certain amount(More)
An improved algorithm has been designed to characterize ligand interactions in organometallic and coordination complexes in terms of the percentage of the metal coordination sphere shielded by a given ligand. The computations for ligand solid angles are performed numerically and employ introduced atomic radii that are larger than covalent but smaller than(More)
The title compound ([3,5-Me(2)bpzaH(2)][AuCl(4)]Cl, 1) (Me(2)bpza=bis(3,5-dimethylpyrazolyl)acetic acid), was prepared by reacting H[AuCl(4)] with 3,5-Me(2)bpza; and spectroscopically and structurally characterized. In the solid state structure of 1, the pyrazolyl ligand is doubly protonated to form two strong charge assisted hydrogen bonds of the type(More)
Glycosylated natural products are reliable platforms for the development of many front-line drugs, yet our understanding of the relationship between attached sugars and biological activity is limited by the availability of convenient glycosylation methods. When a universal chemical glycosylation method that employs reducing sugars and requires no protection(More)
Collagen is an integral part of many types of connective tissue in animals, especially skin, bones, cartilage, and basement membranes. A fibrous protein, collagen has a triple-helical structure, which is comprised of strands with a repeating Xaa-Yaa-Gly sequence. l-Proline (Pro) and 4(R)-hydroxy-l-proline (4-Hyp) residues occur most often in the Xaa and Yaa(More)
We report the first high-resolution structural data for the beta/gamma-peptide 13-helix (i,i+3 C=O...H-N H-bonds), a secondary structure that is formed by oligomers with a 1:1 alternation of beta- and gamma-amino acid residues. Our characterization includes both crystallographic and 2D NMR data. Previous studies suggested that beta/gamma-peptides(More)
Prolyl 4-hydroxylases install a hydroxyl group in the 4R configuration on the gamma-carbon atom of certain (2S)-proline (Pro) residues in tropocollagen, elastin, and other proteins to form (2S,4R)-4-hydroxyproline (Hyp). The gauche effect arising from this prevalent post-translational modification enforces a C(gamma)-exo ring pucker and stabilizes the(More)
The hydroxylation of proline residues in collagen is the most common posttranslational modification in humans. The hydroxylation is stereoselective, affording (2S,4R)-4-hydroxyproline (Hyp) in the Yaa position of the canonical Xaa-Yaa-Gly triad and thereby bestowing marked stabilization upon the collagen triple helix.1 The means by which Hyp stabilizes(More)