Practical Gram-Scale Synthesis of Iboxamycin, a Potent Antibiotic Candidate.

A gram-scale synthesis of iboxamycin, an antibiotic candidate bearing a fused bicyclic amino acid residue, is presented. A pivotal transformation in the route involves an intramolecular hydrosilylation-oxidation sequence to set the ring-fusion stereocenters of the bicyclic scaffold. Other notable features of the synthesis include a high-yielding, highly diastereoselective alkylation of a pseudoephenamine amide, a convergent sp3-sp2 Negishi coupling, and a one-pot transacetalization-reduction reaction to form the target compound's oxepane ring. Implementation of this synthetic strategy has provided ample quantities of iboxamycin to allow for its in vivo profiling in murine models of infection.

Construction of 2,2-Dimethyloxepane Frameworks from Ene-Diols Catalyzed by Metal Catalyst or Brønsted Acid via 7-Endo-Trig Cyclization.

The synthesis of 2,2-dimethyloxepane frameworks based on the 7-endo-trig cyclization of ene-diol using a catalytic amount of metal catalysts (Au, Ag) or Brønsted acid (TfOH) has been developed. Also, the spiro-type dioxabicyclic products were also derived from the diene-diols. For the condition using metal catalysts, the cyclization selectively reacted between the 1,1,3-trisubstituted alkenes and alcohols to form the 2,2-dimethyloxepane frameworks. On the other hand, the TfOH reacted with not only the 1,1,2-trisubstituted alkene, but also the 1-substituted and 1,2-disubstituted alkenes providing the corresponding cyclic ethers, which is quite different from the conditions of the metal catalysts.

Convergent Synthesis of PI3K Inhibitor GDC-0908 Featuring Palladium-Catalyzed Direct C-H Arylation toward Dihydrobenzothienooxepines.

A practical convergent synthesis of PI3K inhibitor GDC-0908 (1) is described. The process features a dihydrobenzothienooxepine formation via palladium-catalyzed intramolecular direct C-H arylation and a Negishi coupling to construct the key C-C bonds. We further developed a general synthesis of dihydrobenzothienooxepines in good to excellent yields via palladium-catalyzed intramolecular direct C-H arylation, which tolerates both electronically and sterically diverse substituents on the phenyl ring.

FeCl3 catalysed 7-membered ring formation in a single pot: a new route to indole-fused oxepines/azepines and their cytotoxic activity.

Various oxepine and azepine fused N-heterocyclic derivatives were synthesized using a new and one-pot reaction of 2,3-dichloro quinoxaline/pyrazine with 2-(1H-indol-2-yl)phenol/aniline in the presence of 25 mol% FeCl3. The reaction proceeded via C-C bond followed by C-X (X = O or N) bond formation to construct the central 7-membered ring, affording the desired products in good yields. The structure assignment was confirmed by the single crystal X-ray analysis of a synthesized oxepine fused N-heterocycle derivative. Most of the synthesized compounds were found to be promising when tested for their anti-proliferative properties against cervical and breast cancer cell lines.

Backbone-Degradable Polymers Prepared by Chemical Vapor Deposition.

Polymers prepared by chemical vapor deposition (CVD) polymerization have found broad acceptance in research and industrial applications. However, their intrinsic lack of degradability has limited wider applicability in many areas, such as biomedical devices or regenerative medicine. Herein, we demonstrate, for the first time, a backbone-degradable polymer directly synthesized via CVD. The CVD co-polymerization of [2.2]para-cyclophanes with cyclic ketene acetals, specifically 5,6-benzo-2-methylene-1,3-dioxepane (BMDO), results in well-defined, hydrolytically degradable polymers, as confirmed by FTIR spectroscopy and ellipsometry. The degradation kinetics are dependent on the ratio of ketene acetals to [2.2]para-cyclophanes as well as the hydrophobicity of the films. These coatings address an unmet need in the biomedical polymer field, as they provide access to a wide range of reactive polymer coatings that combine interfacial multifunctionality with degradability.

Synthesis of pyrimido[4,5-c]azepine- and pyrimido[4,5-c]oxepine-based γ-secretase modulators.

This Letter describes an efficient ring-closing metathesis approach to 2-chloro-4-amino-pyrimido[4,5-c]azepines and 2-chloro-4-amino-pyrimido[4,5-c]oxepines. These chlorides were applied to the synthesis of several potent γ-secretase modulators (GSMs).

A practical and scalable synthesis of carbohydrate based oxepines.

An efficient, seven-step synthesis of carbohydrate based oxepines is reported using per-O-acetyl septanoses as key intermediates. The scope of the synthesis was evaluated by varying both the pyranose starting materials and protecting groups incorporated into the oxepine products. The practicality of the method make it amenable to scale up as demonstrated by the gram-scale synthesis of the d-glucose derived oxepine.

[ANTHELMINTIC SUBSTANCES: MAIN CLASSES, PROBLEMS, TRENDS IN DEVELOPMENT AND PROSPECTS].

The review chronologically considers the main classes of the currently available anthelminthic substances: early anthelmintic compounds, benzimidazoles, imidazolthiazoles, tetrahydropyrimidines, avermectins and milbemycins, and salicylanilides. Great attention is paid to novel substances (emodepside, monepantel, derquantel, tribendimidine) and promising developments. Some aspects of the molecular mechanisms of action of anthelmintics, their resistance, and alternative dehelmintization methods are discussed.

Synthesis of bicyclic proline derivatives by the aza-Cope-Mannich reaction: formal synthesis of (±)-acetylaranotin.

Herein we suggest an approach to oxygenated bicyclic amino acids based on an aza-Cope-Mannich rearrangement. Seven distinct amino acid scaffolds analogous to the natural products were prepared on a gram scale with precise control of stereochemistry. Successful implementation of our strategy resulted in the formal synthesis of acetylaranotin.

An SN1-type Reaction To Form the 1,2-Dioxepane Ring: Synthesis of 10,12-Peroxycalamenene.

The synthesis of the sesquiterpene endoperoxide natural product 10,12-peroxycalamenene has been achieved. Featured transformations include an intramolecular Heck reaction to build the fused bicyclic core and a cobalt-catalyzed peroxidation to install the peroxide functional group. The final step involved an SN1-type ring closure catalyzed by DDQ to construct the 1,2-dioxepane ring.

An antibiotic preorganized for ribosomal binding overcomes antimicrobial resistance.

We report the design conception, chemical synthesis, and microbiological evaluation of the bridged macrobicyclic antibiotic cresomycin (CRM), which overcomes evolutionarily diverse forms of antimicrobial resistance that render modern antibiotics ineffective. CRM exhibits in vitro and in vivo efficacy against both Gram-positive and Gram-negative bacteria, including multidrug-resistant strains of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. We show that CRM is highly preorganized for ribosomal binding by determining its density functional theory-calculated, solution-state, solid-state, and (wild-type) ribosome-bound structures, which all align identically within the macrobicyclic subunits. Lastly, we report two additional x-ray crystal structures of CRM in complex with bacterial ribosomes separately modified by the ribosomal RNA methylases, chloramphenicol-florfenicol resistance (Cfr) and erythromycin-resistance ribosomal RNA methylase (Erm), revealing concessive adjustments by the target and antibiotic that permit CRM to maintain binding where other antibiotics fail.

New short strategy for the synthesis of the dibenz[b,f]oxepin scaffold.

In this report a short and efficient synthesis of the dibenz[b,f]oxepin framework through intramolecular SNAr and McMurry reactions is described. The diaryl ethers required for the McMurry reaction have been obtained in good yields under microwave-assisted conditions of the reaction of salicylaldehydes with fluorobenzaldehydes without catalysts. Application of an intramolecular McMurry reaction to the synthesized diarylethers using TiCl4/Zn in THF gave the target dibenzo[b,f]oxepin system in 53%-55% yields.

Enantioselective total synthesis of (-)-acetylaranotin, a dihydrooxepine epidithiodiketopiperazine.

The first total synthesis of the dihydrooxepine-containing epidithiodiketopiperazine (ETP) (-)-acetylaranotin (1) is reported. The key steps of the synthesis include an enantioselective azomethine ylide (1,3)-dipolar cycloaddition reaction to set the absolute and relative stereochemistry, a rhodium-catalyzed cycloisomerization/chloride elimination sequence to generate the dihydrooxepine moiety, and a stereoretentive diketopiperazine sulfenylation to install the epidisulfide. This synthesis provides access to (-)-1 in 18 steps from inexpensive, commercially available starting materials. We anticipate that the approach described herein will serve as a general strategy for the synthesis of additional members of the dihydrooxepine ETP family.

Total synthesis of (-)-acetylaranotin.

The key step in this total synthesis of (-)-acetylaranotin is the efficient formation of the characteristic dihydrooxepine ring from cyclohexenone through an unusual vinylogous Rubottom oxidation and a regioselective Baeyer-Villiger oxidation. (-)-Acetylaranotin is obtained in 22 steps from commercially available L-Cbz-tyrosine (Cbz=benzyloxycarbonyl).

Total synthesis of (+)-(2'S,3'R)-zoapatanol exploiting the B-alkyl Suzuki reaction and the nucleophilic potential of the sulfinyl group.

A stereoselective synthesis of the diterpenoid oxepane (+)-zoapatanol is described. The key steps include a B-alkyl Suzuki cross-coupling reaction for the stereoselective synthesis of trisubstituted alkenes, creation of the two stereogenic centers on the oxepane ring by heterofunctionalization of an alkene through substrate control exploiting the nucleophilic potential of an intramolecular sulfinyl group, and transformation of a ß-hydroxy sulfoxide into a terminal alkene.

Metal-catalyzed cycloetherification reactions of ß,γ- and γ,δ-allendiols: chemo-, regio-, and stereocontrol in the synthesis of oxacycles.

Versatile routes that lead to a variety of functionalized enantiopure tetrahydrofurans, dihydropyrans, and tetrahydrooxepines are based on chemo-, regio-, and stereocontrolled metal-catalyzed oxycyclization reactions of ß,γ- and γ,δ-allendiols, which were readily prepared from (R)-2,3-O-isopropylideneglyceraldehyde. The application of Pd(II), Pt(II), Au(III), or La(III) salts as the catalysts gives controlled access to differently sized oxacycles in enantiopure form. Usually, chemoselective cyclization reactions occurred exclusively by attack of the secondary hydroxy group (except for the oxybromination of phenyl ß,γ-allenic diols 3b and 3d) to an allenic carbon atom. Regio- and stereocontrol issues are mainly influenced by the nature of the metal catalysts and substituents.

Synthesis of oxepines and 2-branched pyranosides from a d-glucal-derived gem-dibromo-1,2-cyclopropanated sugar.

The conversion of cyclopropane-fused carbohydrates into oxepines is an attractive method for accessing diverse members of the septanoside family of carbohydrate mimetics. 2-Bromooxepines are obtained through silver(I)-promoted thermal ring expansion of a d-glucal-derived gem-dihalocyclopropanated sugar. In contrast, cyclopropane ring cleavage under basic conditions leads to 2-C-branched pyranosides, not the 2-bromooxepine structures assigned in an earlier report.

Design, synthesis and SAR of phenylamino-substituted 5,11-dihydro-dibenzo[a,d]cyclohepten-10-ones and 11H-dibenzo[b,f]oxepin-10-ones as p38 MAP kinase inhibitors.

The p38 MAP kinase is a key enzyme in inflammatory diseases as it is involved in the biosynthesis of proinflammatory cytokines such as TNF-alpha and IL-1beta. Small molecule p38 inhibitors suppress the production of these cytokines and therefore p38 is a promising drug target for novel anti-inflammatory therapeutics. In this study, we report the design, synthesis, and SAR of novel N-substituted 11H-dibenzo[b,f]oxepin-10-ones and 5,11-dihydro-dibenzo[a,d]cyclohepten-10-ones as p38 inhibitors.

Asymmetric synthesis of the ABC-ring system of the antitumor antibiotic MPC1001.

trans-4-Hydroxy-L-proline was converted into a tricyclic compound representing three contiguous rings of the anticancer antibiotic MPC1001. The tricyclic model contains the dihydrooxepin and diketopiperazine subunits, as well as one of the sulfur atoms of the natural product. The diketopiperazine unit was formed by a new method that involves cyclization of an enolate onto the carbonyl of a phenyl carbamate, and the dihydrooxepin ring was generated by using an acid-induced cyclization of an alcohol onto the beta-carbon of a vinylogous amide.

Highly enantioselective carbon-carbon bond formation by Cu-catalyzed asymmetric [2,3]-sigmatropic rearrangement: application to the syntheses of seven-membered oxacycles and six-membered carbocycles.

A concise route for the syntheses of enantioenriched functionalized scaffolds of medium-sized oxacycles and carbocycles employing the chiral auxiliary-mediated Cu-catalyzed ylide formation/[2,3]-sigmatropic rearrangement as a key step was developed.