Building trans-bicyclo[4.4.0]decanes/decenes in complex multifunctional frameworks: the case for antibiotic development

Modular Synthesis of the Potent Antibiotic Amycolamicin and Diastereomeric Analogues Thereof

A modular approach to the potent, broad-spectrum antibiotic amycolamicin and seven diastereomeric analogues is described. The synthesis features bioinspired construction of the high-carbon amycolose segment, gold(I)-catalyzed high-yielding O-glycosylation of the trans-decalin scaffold, N-glycosylation of the bromoacetylated l-valine derivative, and condition-tuned late-stage C-acylation of the tetramic acid motif. An assessment of the antibacterial properties of these synthetic molecules indicated that the correct stereochemistry is essential for the potent bioactivity of amycolamicin.

Discovery, Biosynthesis, Total Synthesis, and Biological Activities of Solanapyrones: [4 + 2] Cycloaddition-Derived Polyketides of Fungal Origin

Solanapyrones are metabolites bearing a 3,4-dehydrodecalin moiety isolated from cultures of different fungi that are associated with plant diseases. Research on solanapyrones resulted in the first report of a Diels-Alderase enzyme implicated in natural product biosynthesis related to the formation of the 3,4-dehydrodecalin core. In addition, several total syntheses of solanapyrones have been reported, which are also connected with the formation of the characteristic cycloaddition-derived 3,4-dehydrodecalin moiety. This Review provides the first comprehensive overview on the chemistry, biosynthesis, and biological activities of solanapyrones under the theme of synthetic and biosynthetic research progress on cycloaddition-derived secondary metabolites.

Remote proton elimination: C-H activation enabled by distal acidification

Generally, the acidity of carbon-hydrogen bonds is most sensitive to functionality just one or two bonds away. Here, we present an approach to the formation of carbon-carbon σ bonds by remote proton elimination, a distinct mode of carbon-hydrogen activation enabled by distal acidification through five carbon-carbon bonds. Application of remote proton elimination to cyclodecyl cations unveiled an appealing method for the synthesis of decalins. The transformation is regioconvergent, proceeds without the need for a directing group or precious metal, and demonstrates exquisite site selectivity. An in-depth computational study illuminated the reaction mechanism. Additionally, we describe the complete stereoisomeric enrichment of the decalin products through epimerization mediated by hydrogen atom transfer.

Structural Analysis of the Michael-Michael Ring Closure (MIMIRC) Reaction Products

A representative number of decalin and hydrindane derivatives 2a-l were prepared in 11-91% yield by means of a cascade reaction of cyclohexanone/cyclopentanone enolates and methyl acrylate through a Michael-Michael ring closure (MIMIRC) process. The relative stereochemistry of the four stereogenic centers formed in all products was determined by analyzing the vicinal coupling constants from the 1H NMR and X-ray crystallography. Such a stereochemical outcome was corroborated by conformational analysis supported by DFT calculations and simulating the 1H NMR spectra of representative products. All products showed the same relative stereochemistry at C-1 and C-8a, while at C-3 and bridgehead carbon C-4a, configurational changes were observed. The present results provide some insights about the scope and limitations of the triple cascade reaction between cycloalkanone enolates with methyl acrylate. This synthetic protocol is still a simple and very practical alternative to generate decalin and hydrindane derivatives with great structural diversity.