beta-Peptides: from structure to function.

NMR spectroscopy in the structural elucidation of oligosaccharides and glycosides.

High resolution proton magnetic resonance spectroscopy of biological fluids

The principal secondary structural motifs adopted by peptides assembled from beta-amino acid units are discussed: the 14-, 12-, 10-, 12/10-, and 8-helices, as well as the hairpin turn, extended structures, stacks, and sheets. Features that promote a particular folding propensity are outlined and illustrated by structures determined in solution (NMR) and in the solid-state (x-ray). The N-C(beta)-C(alpha)-CO dihedral angles from molecular dynamics simulations, which are indicative of a particular secondary structure, are presented. A brief description of a helix and a turn of gamma-peptides is also given.

Helices and other secondary structures of β‐ and γ‐peptides

Biosynthesis of polyketide synthase extender units

Characterization of a Water-Soluble, Helical β-Peptide

Proteasome-inhibitory and cytotoxic constituents of Garcinia lateriflora: absolute configuration of caged xanthones

Reaction of (tetrahydrofuran)borane with dihydridotridecacarbonyl- and tetrahydridododecacarbonyltetraruthenate: preparation and structure of the tetraruthenium butterfly cluster HRu4(CO)12BH2

Feeding experiments with [U-13C3]- and (2R)-[1-2H2]glycerol showed that glycerol is incorporated intact into carbon atoms 22, 23 and 24 of the aglycone of chlorothricin. C-1 of glycerol gives rise to C-22 with retention of one atom of deuterium, which occupies the H-22R position. A mechanism for the assembly of the aglycone is proposed which invokes phosphoenolpyruvate as the direct precursor of the 3-carbon moiety and a Baeyer-Villiger oxidation as the mode of formation of the macrocyclic lactone functionality. A feeding experiment with [1, 2-13C2]succinate suggests that the propionate units of the aglycone polyketide are formed entirely via the methylmalonyl-CoA mutase reaction. The formation of the two 2, 6-dideoxy-D-rhamnose moieties of chlorothricin from glucose was shown to involve replacement of the 2-hydroxyl group of the sugar by hydrogen with inversion of configuration at C-2. This contrasts with the retention stereochemistry observed earlier for the analogous formation of the 2, 6-dideoxyhexose moiety of the antibiotic granaticin.

Further studies on the biosynthesis of chlorothricin.

An inexpensive, versatile sample illuminator for photo-CIDNP on any NMR spectrometer

Charles E. Cottrell

Papers

Characterization of a Water-Soluble, Helical β-Peptide

Proteasome-inhibitory and cytotoxic constituents of Garcinia lateriflora: absolute configuration of caged xanthones

Reaction of (tetrahydrofuran)borane with dihydridotridecacarbonyl- and tetrahydridododecacarbonyltetraruthenate: preparation and structure of the tetraruthenium butterfly cluster HRu4(CO)12BH2

Further studies on the biosynthesis of chlorothricin.

An inexpensive, versatile sample illuminator for photo-CIDNP on any NMR spectrometer