Total synthesis of AI-77-B

Concise synthesis of amino acid component of amicoumacins via dihydrooxazine formation through intramolecular conjugate addition

Amicoumacins are a family of antibiotics with a variety of important bioactivities. A concise and efficient method was developed for synthesizing the amino acid component of amicoumacins via the corresponding dihydrooxazine intermediate. The dihydrooxazine ring was formed with complete stereoselectivity through an intramolecular conjugate addition of a δ-trichloroacetimidoyloxy-α,β-unsaturated ester, which was obtained from a known 4,6-O-p-methoxybenzylidene-protected d-glucose. The synthesis developed in this study can be used to synthesize the building blocks of amicoumacins and can likely be adapted for the synthesis of other types of molecules possessing dihydrooxazine rings or amino alcohol moieties.

Multivalent Pyrrolidine Iminosugars: Synthesis and Biological Relevance

Recently, the strategy of multivalency has been widely employed to design glycosidase inhibitors, as glycomimetic clusters often induce marked enzyme inhibition relative to monovalent analogs. Polyhydroxylated pyrrolidines, one of the most studied classes of iminosugars, are an attractive moiety due to their potent and specific inhibition of glycosidases and glycosyltransferases, which are associated with many crucial biological processes. The development of multivalent pyrrolidine derivatives as glycosidase inhibitors has resulted in several promising compounds that stand out. Herein, we comprehensively summarized the different synthetic approaches to the preparation of multivalent pyrrolidine clusters, from total synthesis of divalent iminosugars to complex architectures bearing twelve pyrrolidine motifs. Enzyme inhibitory properties and multivalent effects of these synthesized iminosugars were further discussed, especially for some less studied therapeutically relevant enzymes. We envision that this comprehensive review will help extend the applications of multivalent pyrrolidine iminosugars in future studies.

Application of Pd-Catalyzed C-H Alkylation Reaction in Total Syntheses of Twelve Amicoumacin-Type Natural Products

Enantioselective total syntheses of 12 amicoumacin-type natural products are accomplished with a palladium(II)-catalyzed C-H alkylation as the key step to furnish the 3,4-dihydroisocoumarin scaffold. The target chemicals are assembled in a convergent protocol by merging 3,4-dihydroisocoumarin derived amine part with categories of acid segments that are efficiently prepared by chemoselective catalytic oxidation of chiral 1,2-dihydroxyethylfuran-2(5H)-ones. Afterward, the cytotoxicity of amicoumacins on five cancer cell lines and one normal cell line is investigated.

Asymmetric Total Synthesis of Hetiamacins A-F

Herein, we report a concise and stereoselective approach for the asymmetric total synthesis of hetiamacins A-F on the basis of the total synthesis of amicoumacin C, which could be synthesized from a known l-aspartic acid derivative. The synthesis of hetiamacin A was accomplished by an 11-step sequence that featured 1,3-oxazinane ring formation of amicoumacin B followed by amidation in one pot. Hetiamacins B-F were synthesized from amicoumacin A in only one step.

3,4-Dihydroisocoumarins, Interesting Natural Products: Isolation, Organic Syntheses and Biological Activities

BACKGROUND

3,4-dihydroisocoumarins are an important small group belonging to the class of naturally occurring lactones isolated from different bacterial strains, molds, lichens, and plants. The structures of these natural compounds show various types of substitution in their basic skeleton and this variability influences deeply their biological activities. These lactones are structural subunits of several natural products and serve as useful intermediates in the synthesis of different heterocyclic molecules, which exhibit a wide range of biological activities, such as anti-inflammatory, antiplasmodial, antifungal, antimicrobial, antiangiogenic and antitumoral activities, among others. Their syntheses have attracted attention of many researchers reporting many synthetic strategies to achieve 3,4-dihydroisocoumarins and other related structures.

OBJECTIVE

In this context, the isolation of these natural compounds from different sources, their syntheses and biological activities are reviewed, adding the most recent advances and related developments.

CONCLUSION

This review aims to encourage further work on the isolation and synthesis of this class of natural products. It would be beneficial for synthetic as well as the medicinal chemists to design selective, optimized dihydroisocoumarin derivatives as potential drug candidates, since dihydroisocoumarin scaffolds have significant utility in the development of therapeutically relevant and biologically active compounds.

Exploring the divalent effect in fucosidase inhibition with stereoisomeric pyrrolidine dimers

Multi-valent inhibitors offer promise for the enhancement of therapeutic compounds across a range of chemical and biological processes. Here, a significant increase in enzyme-inhibition potencies was observed with a dimeric iminosugar-templated fucosidase inhibitor (IC50 = 0.108 μM) when compared to its monovalent equivalent (IC50 = 2.0 μM). Such a gain in binding is often attributed to a "multivalent effect" rising from alternative recapture of the scaffolded binding epitopes. The use of control molecules such as the meso analogue (IC50 = 0.365 μM) or the enantiomer (IC50 = 569 μM), as well as structural analysis of the fucosidase-inhibitor complex, allowed a detailed analysis of the possible mechanism of action, at the molecular level. Here, the enhanced binding affinity of the dimer over the monomer can be attributed to additional interactions in non-catalytic sites as also revealed in the 3-D structure of a bacterial fucosidase inhibitor complex.