Gold-Catalyzed Unexpected Ring Transformation of Pyrimidodiazepine Derivatives.

Pyrimidodiazepine derivatives underwent an unexpected gold-catalyzed retro-Mannich-type carbon-carbon bond cleavage and intramolecular nucleophilic cyclization. The pyrimidodiazepines bearing an alkyne moiety showed novel orthogonal reactivity in the presence of a gold catalyst, as opposed to the alkynophilicity that is commonly observed with gold catalysts. The ring transformation reaction of pyrimidodiazepines probably proceeds through an acyclic iminium intermediate.

Diversity-oriented synthetic strategy for developing a chemical modulator of protein-protein interaction.

Diversity-oriented synthesis (DOS) can provide a collection of diverse and complex drug-like small molecules, which is critical in the development of new chemical probes for biological research of undruggable targets. However, the design and synthesis of small-molecule libraries with improved biological relevance as well as maximized molecular diversity represent a key challenge. Herein, we employ functional group-pairing strategy for the DOS of a chemical library containing privileged substructures, pyrimidodiazepine or pyrimidine moieties, as chemical navigators towards unexplored bioactive chemical space.

Aerobic oxygenative cleavage of electron deficient C-C triple bonds in the gold-catalyzed cyclization of 1,6-enynes.

Gold-catalyzed aerobic oxygenative cleavage of triple bonds that occurs under the ambient pressure of air and at room temperature is reported; radical inhibition tests suggest that oxygenation occurs via a gold-bound metalloradical intermediate.

Synthesis and library construction of privileged tetra-substituted Δ5-2-oxopiperazine as β-turn structure mimetics.

In this study, we developed an efficient and practical procedure for the synthesis of tetra-substituted Δ5-2-oxopiperazine that mimics the bioactive β-turn structural motif of proteins. This synthetic route is robust and modular enough to accommodate four different substituents to obtain a high level of molecular diversity without any deterioration in stereochemical enrichment of the natural and unnatural amino acids. Through the in silico studies, including a distance calculation of side chains and a conformational overlapping of our model compound with a native β-turn structure, we successfully demonstrated the conformational similarity of tetra-substituted Δ5-2-oxopiperazine to the β-turn motif.

Gold-catalyzed intermolecular reactions of propiolic acids with alkenes: [4 + 2] annulation and enyne cross metathesis.

A gold-catalyzed intermolecular reaction of propiolic acids with alkenes led to a [4 + 2] annulation or enyne cross metathesis. The [4 + 2] annulation proceeds with net cis-addition with respect to alkenes and provides an expedient route to α,β-unsaturated δ-lactones, for which preliminary asymmetric reactions were also demonstrated. For 1,2-disubstituted alkenes, unprecedented enyne cross metathesis occurred to give 1,3-dienes in a completely stereospecific fashion.