Amide Activation in Ground and Excited States

Not all amide bonds are created equally. The purpose of the present paper is the reinterpretation of the amide group by means of two concepts: amidicity and carbonylicity. These concepts are meant to provide a new viewpoint in defining the stability and reactivity of amides. With the help of simple quantum-chemical calculations, practicing chemists can easily predict the outcome of a desired process. The main benefit of the concepts is their simplicity. They provide intuitive, but quasi-thermodynamic data, making them a practical rule of thumb for routine use. In the current paper we demonstrate the performance of our methods to describe the chemical character of an amide bond strength and the way of its activation methods. Examples include transamidation, acyl transfer and amide reductions. Also, the method is highly capable for simple interpretation of mechanisms for biological processes, such as protein splicing and drug mechanisms. Finally, we demonstrate how these methods can provide information about photo-activation of amides, through the examples of two caged neurotransmitter derivatives.

Utilizing DART mass spectrometry to pinpoint halogenated metabolites from a marine invertebrate-derived fungus

Prenylated indole alkaloids are a diverse group of fungal secondary metabolites and represent an important biosynthetic class. In this study we have identified new halogenated prenyl-indole alkaloids from an invertebrate-derived Malbranchea graminicola strain. Using direct analysis in real time (DART) mass spectrometry, these compounds were initially detected from hyphae of the fungus grown on agar plates, without the need for any organic extraction. Subsequently, the metabolites were isolated from liquid culture in artificial seawater. The structures of two novel chlorinated metabolites, named (-)-spiromalbramide and (+)-isomalbrancheamide B, provide additional insights into the assembly of the malbrancheamide compound family. Remarkably, two new brominated analogues, (+)-malbrancheamide C and (+)-isomalbrancheamide C, were produced by enriching the growth medium with bromine salts.

Concise enantioselective synthesis of ent-malbrancheamide B

A concise enantioselective synthesis of the fungal metabolite ent-malbrancheamide B was accomplished through the union of a C-prenylated proline derivative and a substituted indole pyruvic acid SEM enol ether, followed by a cationic double cyclization as the key step.

Calmodulin inhibitory activity of the malbrancheamides and various analogs

The preparation and biological activity of various structural analogs of the malbrancheamides are disclosed. The impact of indole chlorination, C-12a relative stereochemistry, and bicyclo[2.2.2]diazaoctane core oxidation state on the ability of these analogs to inhibit calmodulin dependent phosphodiesterase (PDE1) was studied, and a number of potent compounds were identified.

Improved Biomimetic Total Synthesis of d,l-Stephacidin A

The direct conversion of beta-hydroxyproline derivatives into 5-hydroxypyrazin-2(1H)-ones under Mitsunobu conditions has been discovered to be a general biomimetic protocol generating IMDA intermediates and has been applied to the concise, biomimetic total syntheses of D,L-stephacidin A and D,L-brevianamide B.