Catalytic, Enantioselective Syn-Oxyamination of Alkenes.

The chemo-, regio-, diastereo-, and enantioselective 1,2-oxyamination of alkenes using selenium(II/IV) catalysis with a chiral diselenide catalyst is reported. This method uses N-tosylamides to generate oxazoline products that are useful both as protected 1,2-amino alcohol motifs and as chiral ligands. The reaction proceeds in good yields with excellent enantio- and diastereoselectivity for a variety of alkenes and pendant functional groups such as sulfonamides, alkyl halides, and glycol-protected ketones. Furthermore, the rapid generation of oxazoline products is demonstrated in the expeditious assembly of chiral PHOX ligands as well as diversely protected amino alcohols.

A Peptoid Square Helix via Synergistic Control of Backbone Dihedral Angles.

The continued expansion of the fields of macromolecular chemistry and nanoscience has motivated the development of new secondary structures that can serve as architectural elements of innovative materials, molecular machines, biological probes, and even commercial medicines. Synthetic foldamers are particularly attractive systems for developing such elements because they are specifically designed to facilitate synthetic manipulation and functional diversity. However, relatively few predictive design principles exist that permit both rational and modular control of foldamer secondary structure, while maintaining the capacity for facile diversification of displayed functionality. We demonstrate here that the synergistic application of two such principles in the design of peptoid foldamers yields a new and unique secondary structure that we term an "η-helix" due to its repeating turns, which are highly reminiscent of peptide ß-turns. Solution-phase structures of η-helices were obtained by simulated annealing using NOE-derived distance restraints, and the NMR spectra of a series of designed η-helices were altogether consistent with the primary adoption of this structure. The structure is resilient to solvent and temperature changes, and accommodates diversification without requiring postsynthetic manipulation. The unique shape, broad structural stability, and synthetic accessibility of η-helices could facilitate their utilization in a wide range of applications.

Tandem Incorporation of Enantiomeric Residues Engenders Discrete Peptoid Structures.

A new peptoid design strategy entailing the concurrent inclusion of enantiomeric side chains enabled the construction of several new structural motifs, including a newly characterized "ω-strand". This new architectural technique significantly expands peptoid structural and functional space and can potentially be applied to other foldameric systems.