Large Scale Synthesis of Native Turn and Helix Mimics Stabilized by a Generic Hydrogen Bond Surrogate

Short Turn and Helix mimics frequently represent molecular recognition surfaces perturbing bio-relevant protein-biomolecular interfaces. Generic methods that can stabilize short peptides into turns or helices by retaining all recognition elements, have tremendous applications in drug discovery. Here, a versatile modular synthetic protocol is presented for stabilizing turns and helices of different sizes by replacing their ring-closing hydrogen bonds with a generic three-carbon covalent surrogate. Two Fukuyama-Mitsunobu reactions insert the surrogate between desired residues in high yields and purity. Coupling with turn size-dependent oligopeptides containing both sterically restricted and non-coded residues, followed by macrolactamization yield a variety of stabilized turns. Short peptide extensions at the C-terminus of these turns yield stabilized 310-helices and α-helices. This solution-phase synthetic approach provides combinatorial access to libraries of stabilized turns and helices with all their native residues retained, in >100 mmole scales, in about one week per stabilized mimic, to technicians with postgraduate level training.

Heterogeneous Organo- and Metal Catalysis Using Phosphine Oxide Derivatives Anchored on Multiwalled Carbon Nanotubes

Oxidized multiwalled carbon nanotubes were modified anchoring phosphine oxides and used as heterogeneous catalysts. A proper substitution of the phosphine oxides allowed the use of the Tour reaction and the nitrene cycloaddition to obtain functionalized carbon nanotubes (CNT) with a loading up to 0.73 mmol/g of material. The catalysts proved efficient in Wittig reactions, Mitsunobu reactions, and Staudinger ligations. Furthermore, the phosphorus decorated CNT were used to produce nanocomposite with Pd nanoparticles able to catalyze Heck reactions.

Hydrazine derivative synthesis by trifluoroacetyl hydrazide alkylation

N′-Alkyl hydrazides were effectively synthesized by routes featuring installation, alkylation, and removal of a trifluoroacetyl group. A set of amino acid derived hydrazides were acylated using trifluoroacetic anhydride, and the resulting trifluoroacetyl hydrazides were alkylated with alcohols in Mitsunobu reactions and with alkyl halides under alkaline conditions. Removal of the trifluoroacetyl group was affected under reductive and hydrolytic conditions to provide the respective N′-alkyl hydrazides. This three-step process may be performed without isolation of intermediates to yield N′-alkyl hydrazide after a single chromatographic purification.

Glycosylation with ulosonates under Mitsunobu conditions: scope and limitations

Mitsunobu reactions on highly hindered tertiary type hydroxy groups of ulosonates: from 47 NuH compounds O-, N-, and S-nucleophiles gave the corresponding ulosidonates in 30–78% yields, while C-nucleophiles were unreactive.

Redox-neutral organocatalytic Mitsunobu reactions

Nucleophilic substitution reactions of alcohols are among the most fundamental and strategically important transformations in organic chemistry. For over half a century, these reactions have been achieved by using stoichiometric, and often hazardous, reagents to activate the otherwise unreactive alcohols. Here, we demonstrate that a specially designed phosphine oxide promotes nucleophilic substitution reactions of primary and secondary alcohols in a redox-neutral catalysis manifold that produces water as the sole by-product. The scope of the catalytic coupling process encompasses a range of acidic pronucleophiles that allow stereospecific construction of carbon-oxygen and carbon-nitrogen bonds.

The catalytic Mitsunobu reaction: a critical analysis of the current state-of-the-art

This Review article provides a summary and critical metrics-based analysis of recently developed catalytic Mitsunobu reactions.