Modification of Bafilomycin Structure to Efficiently Synthesize Solid-State NMR Probes that Selectively Bind to Vacuolar-Type ATPase

Total Synthesis and Bioactivity Profile of (+)-Ieodomycins A and B and their Stereoisomers

Herein, we report the first- and second-generation syntheses of (+)-ieodomycins A and B and their stereoisomers via the late-stage elaboration of their conjugated E-diene side chains. Key steps for successful synthesis included Keck asymmetric allylation to introduce a hydroxyl group at the C5 position, consecutive Wipf's carboalumination modification, iodination, Sharpless asymmetric dihydroxylation, one-carbon homologation via cyanation, Mukaiyama lactonization, and Stille cross-coupling to form the conjugated E-diene moiety. Further, the preliminary in vitro bioactivity profile against various disease-related molecular targets and cell lines was investigated. Results indicated that compounds 30b and 30c, diastereoisomers of (+)-ieodomycin B (2), serve as α-glucosidase inhibitors, while compounds 30b and 30d inhibit the angiotensin-converting enzyme.

Golgi-Targeting Anticancer Natural Products

The Golgi apparatus plays an important role in maintaining cell homeostasis by serving as a biosynthetic center for glycans, lipids and post-translationally modified proteins and as a sorting center for vesicular transport of proteins to specific destinations. Moreover, it provides a signaling hub that facilitates not only membrane trafficking processes but also cellular response pathways to various types of stresses. Altered signaling at the Golgi apparatus has emerged as a key regulator of tumor growth and survival. Among the small molecules that can specifically perturb or modulate Golgi proteins and organization, natural products with anticancer property have been identified as powerful chemical probes in deciphering Golgi-related pathways and, in particular, recently described Golgi stress response pathways. In this review, we highlight a set of Golgi-targeting natural products that enabled the characterization of the Golgi-mediated signaling events leading to cancer cell death and discuss the potential for selectively exploiting these pathways for the development of novel chemotherapeutic agents.

A Comparative Synthetic Strategy Perspective on α-Amino Acid- and Non-Amino Acid-Derived Synthons towards Total Syntheses of Selected Natural Macrolides

Macrocyclic alkaloids (macrolides) and cyclopeptides have an immense range of applications in drug discovery research because of their natural abundance and potential biological and physicochemical properties. Presently, more than 100 approved drugs or clinical drug candidates contain macrocyclic scaffolds as the biologically active component. This review provides an interesting perspective about the use of amino acid-derived chiral pools versus other methods derived from miscellaneous synthons towards the total synthesis of non-peptidic macrolides. The synthetic routes and the key strategies involved in the total syntheses of ten natural macrolides have been discussed. Both the amino acid-derived and non-amino acid-derived synthetic routes have been illustrated to present a comparative study between the two approaches.

Clarithromycin decreases rhinovirus replication and cytokine production in nasal epithelial cells from subjects with bronchial asthma: effects on IL-6, IL-8 and IL-33

Rhinoviral infection is associated with an increased risk of asthma attacks. The macrolide clarithromycin decreases cytokine production in nasopharyngeal aspirates from patients with wheezing, but the effects of macrolides on cytokine production in nasal epithelial cells obtained from asthmatic subjects remain unclear. Here, human nasal epithelial cells were infected with type-14 rhinovirus (RV14), a major RV group. Titers and RNA of RV14 and cytokine concentrations, including IL-1β and IL-6, were higher in the supernatants of the cells obtained from subjects with bronchial asthma (asthmatic group) than in those from the non-asthmatic group. Pretreatment with clarithromycin decreased RV14 titers, viral RNA and cytokine concentrations, and susceptibility to RV14 infection. Pretreatment with clarithromycin also decreased IL-33 production, which was detected after infection. Pretreatment with clarithromycin decreased the expression of intercellular adhesion molecule-1, the receptor for RV14, after infection, the number and fluorescence intensity of the acidic endosomes through which RV RNA enters the cytoplasm, and the activation of nuclear factor kappa-B proteins in nuclear extracts. These findings suggested that RV replication and cytokine production may be enhanced in nasal epithelial cells obtained from subjects with bronchial asthma and may be modulated by clarithromycin.

Separation of Alkyne Enantiomers by Chiral Column HPLC Analysis of Their Cobalt-Complexes

Separation of the enantiomers of new chiral alkynes in strategic syntheses and bioorthogonal studies is always problematic. The chiral column high-performance liquid chromatography (HPLC) method in general could not be directly used to resolve such substrates, since the differentiation of the alkyne segment with the other alkane/alkene segment is not significant in the stationary phase, and the alkyne group is not a good UV chromophore. Usually, a pre-column derivatization reaction with a tedious workup procedure is needed. Making use of easily-prepared stable alkyne-cobalt-complexes, we developed a simple and general method by analyzing the in situ generated cobalt-complex of chiral alkynes using chiral column HPLC. This new method is especially suitable for the alkynes without chromophores and other derivable groups.