A Hendecad Motif Is Preferred for Heterochiral Coiled-Coil Formation.

The structural principles that govern interactions between l- and d-peptides are not well understood. Among natural proteins, coiled-coil assemblies formed between or among α-helices are the most regular feature of tertiary and quaternary structures. We recently reported the first high-resolution structures for heterochiral coiled-coil dimers, which represent a starting point for understanding associations of l- and d-polypeptides.

High-resolution structures of a heterochiral coiled coil.

Interactions between polypeptide chains containing amino acid residues with opposite absolute configurations have long been a source of interest and speculation, but there is very little structural information for such heterochiral associations. The need to address this lacuna has grown in recent years because of increasing interest in the use of peptides generated from d amino acids (d peptides) as specific ligands for natural proteins, e.g.

Catalytic oxidative cleavage of olefins promoted by osmium tetroxide and hydrogen peroxide.

Hydrogen peroxide was employed as the terminal oxidant in the osmium tetroxide mediated oxidative cleavage of olefins, producing the corresponding aldehyde and ketone products. Aryl olefins are cleaved in good to excellent yield regardless of arene electronics. Alkyl olefins cleave in moderate to good yield for di- and tri-substituted alkenes.

Direct oxidative cleavage of alpha- and beta-dicarbonyls and alpha-hydroxyketones to diesters with KHSO5.

Presented is a methodology to oxidatively cleave alpha-hydroxyketones and alpha- or beta-diones using the environmentally benign reagent KHSO(5), prepared easily from Oxone, to diesters in one simple transformation. In addition, we undertook a mechanistic study to provide a plausible mechanistic interpretation. These reactions may prove to be valuable alternatives to other related metal-mediated processes.

Direct lactonization of alkenols via osmium tetroxide-mediated oxidative cleavage.

[reaction: see text] A highly efficient, mild, and simple protocol is presented for the tandem OsO(4)-mediated oxidative cleavage/oxidative lactonization of alkenols to lactones. The protocol couples the OsO(4)-catalyzed oxidative cleavage of olefins with Oxone as the co-oxidant with the direct oxidation of aldehydes in alcoholic solvents to their corresponding esters.

Facile oxidation of aldehydes to acids and esters with Oxone.

[reaction: see text] A highly efficient, mild, and simple protocol is presented for the oxidation of aldehydes to carboxylic acids utilizing Oxone as the sole oxidant. Direct conversion of aldehydes in alcoholic solvents to their corresponding ester products is also reported. These reactions may prove to be valuable alternatives to traditional metal-mediated oxidations.

Osmium tetroxide-promoted catalytic oxidative cleavage of olefins: an organometallic ozonolysis.

A mild, organometallic alternative to ozonolysis utilizing oxone and OsO(4) is presented. This is a direct oxidation of olefins via the carbon-carbon cleavage of an osmate ester by the action of oxone. Twenty-four different olefins were converted to their corresponding ketones or carboxylic acids in high yields (>80%).