The selective N- or O-alkylation of 4-(trihalomethyl)-pyrimidin-2(1H)-ones, using 5-bromo enones/enaminones as alkylating agents, is reported. It was found that the selectivity toward the N-or O-regioisomer is driven by the substituent present at the 6-position of the pyrimidine ring, thus enabling the preparation of each isomer as the sole product, in 60−95% yields. Subsequent cyclocondensation of the enaminone moiety with nitrogen dinucleophiles led to pyrimidine−azole conjugates in 55−83% yields.

Rosellin A and B, two red diketopiperazine alkaloids with unprecedented structures, have been isolated from the fruiting bodies of the mushroom Mycena rosella. The structures of the rosellins were mainly deduced from their 2D NMR and HRMS (ESI) spectra. Their absolute configuration was determined by comparison of the CD spectra of the rosellins with the corresponding CD spectra obtained by quantum chemical calculations. Root exposure to rosellin A led to bleaching of the leaves of Lepidium sativum plants.

Four new hygrophorones (1–4) together with the known hygrophorone B12 (5) have been isolated from fruiting bodies of the basidiomycete Hygrophorus abieticola Krieglst. ex Gröger & Bresinsky. Their structures were assigned on the basis of extensive one and two dimensional NMR spectroscopic analyses as well as ESI-HRMS measurements. Among these compounds, two previously undescribed hygrophorone types, named hygrophorone H12 (3) and 2,3-dihydrohygrophorone H12 (4), were identified. The absolute configuration of hygrophorone E12 (2) is suggested based on quantum chemical CD calculations, while a semisynthetic approach in conjunction with computational studies and analysis of NOE interactions allowed the stereochemical assignment of compounds 3 and 4. Additionally, semisynthetic derivatives of hygrophorone B12 (5) were generated by acetylation of the hydroxyl groups. The biological activity of the natural and semisynthetic hygrophorones was evaluated against phytopathogenic organisms, revealing that the α,β-unsaturated carbonyl functionality is likely to be an essential structural feature. Hygrophorone B12 (5) was identified as the most active compound, acting against both ascomycetous fungi and oomycetes.

Peptide ligation and macrocyclization are among the most relevant approaches in the field of peptide chemistry. Whereas a variety of strategies relying on coupling reagents and native chemical ligation are available, there is a continuous need for efficient peptide ligation and cyclization methods. Herein we report on the utilization of convertible isonitriles as effective synthetic tools for the ligation and macrocyclization of peptides arising from isocyanide-based multicomponent reactions. The strategy relies on the use of convertible isonitriles—derived from Fukuyama amines—and peptide carboxylic acids in Ugi and Passerini reactions to afford N-alkylated peptides and depsipeptides, respectively, followed by conversion of the C-terminal amide onto either N-peptidoacyl indoles or pyrroles. Such activated peptides proved efficient in the ligation to peptidic, lipidic and fluorescently labeled amines and in macrocyclization protocols. As a result, a wide set of N-substituted peptides (with methyl, glycosyl and amino acids as N-substituents), cyclic N-methylated peptides and a depsipeptide were produced in good yields using conditions that involve either classical heating or microwave irradiation. This report improves the repertoire of peptide covalent modification methods by exploiting the synthetic potential of multicomponent reactions and convertible isonitriles.

The cyclization of peptide side chains has been traditionally used to either induce or stabilize secondary structures (β-strands, helices, reverse turns) in short peptide sequences. So far, classic peptide coupling, nucleophilic substitution, olefin metathesis, and click reactions have been the methods of choice to fold synthetic peptides by means of macrocyclization. This article describes the utilization of the Ugi reaction for the side chain-to-side chain and side chain-to-termini macrocyclization of peptides, thus enabling not only access to stable folded structures but also the incorporation of exocyclic functionalities as N-substituents. Analysis of the NMR-derived structures revealed the formation of helical turns, β-bulges, and α-turns in cyclic peptides cross-linked at i, i + 3 and i, i + 4 positions, proving the folding effect of the multicomponent Ugi macrocyclization. Molecular dynamics simulation provided further insights on the stability and molecular motion of the side chain cross-linked peptides.

An efficient and convenient method was developed for the regioselective formation of 2-aryl- or 2,5-diarylselenophenes via a palladium-catalyzed direct arylation. This protocol is suitable for a wide range of aryl halides containing different functional groups. The 2-arylated substrates can undergo an additional regioselective direct arylation event furnishing symmetrical or unsymmetrical 2,5-diaryl selenophenes in good yield. Competition experiments and the role of the acid additive are in agreement with a concerted metalation deprotonation (CMD) pathway.

A highly convergent and stereocontrolled synthesis of epothilone D (4) is reported. Key features are a cheap and Z-selective synthesis of the northern half based on nerol and acetoacetate and chromium(II)-mediated Reformatsky reactions as a powerful tool for chemoselective asymmetric carbon–carbon bond formations, including an unusual stereospecific macroaldolization.

Multiple multicomponent macrocyclizations including bifunctional buildings blocks (MiBs) so far have relied almost exclusively on Ugi reactions. The efficient expansion to non-Ugi-MiBs is exemplified by the synthesis of tetra-β-lactam and bis-α-acyloxy carboxamide macrocycles based on multiple Staudinger and Passerini three-component reactions (3CR), respectively. A recent variation of the Passerini-3CR that involves primary alcohols, isocyanides, and carboxylic acids under oxidative conditions is successfully adapted to this procedure.

Bile acids are important scaffolds in medicinal and supramolecular chemistry. However, the use of seco bile acids, i.e., bile acids with opened rings, as cores or building blocks for the assembly of complex peptide conjugates or macrocycles has remained elusive so far. A biomimetic approach to secocholanes, based on an oxidative ring-expansion/ring-opening sequence, offers efficient access to novel structures with tunable flexibility and functionality. The process preserves selected portions of the original stereochemical and functional information of the steroid, while additional structural elements are incorporated in further (diversity-generating) steps. The potential of these building blocks for peptide and macrocycle chemistry is exemplified by the attachment of relevant α-amino acids and by the production of various complex macrocycles obtained by conventional (e.g., macrolactonization and macrolactamization) and multicomponent (e.g., Ugi four-component) macrocyclizations. This combination of secocholanic skeleton manipulation with, e.g., varied types of macrocyclization protocols, produces high levels of skeletal diversity and complexity. Therefore, this approach may have applicability either for the synthesis of biologically active ligands or as artificial receptors (“hosts”).

The formation and 2-amino alcohol catalyzed addition of arylzinc reagents from and with boronic acids, respectively, is drastically accelerated to a few minutes under microwave irradiation without loss of enantioselectivity (up to 98% ee). Of the amino acid derived catalysts tested, the conformationally restricted bulky substituted aziridine-2-methanols derived from serine show the best overall performance in the formation of diarylmethanols.