Intramolecular Olefin Metathesis Research Articles

Synthesis and evaluation of ent-Conduramine C-1 derivatives as α-glucosidase inhibitors via CSI-mediated amination reaction

Concise synthesis of ent-conduramine C-1 and its derivatives has been achieved by using commercially available d-ribose. The key steps in the synthesis are regioselective and diastereoselective amination of polybenzyl ethers by chlorosulfonyl isocyanate (CSI), chelation-controlled carbonyl addition, and intramolecular olefin metathesis. All of the synthesized compounds were evaluated for inhibitory activity against α-glucosidase. The derivatives 18 (IC50 = 0.65 ± 0.03 mM) and 19 (IC50 = 0.26 ± 0.01 mM) were identified to be more potent than well-known α-glucosidase inhibitor acarbose (IC50 = 1.05 ± 0.17 mM) as a positive control.

Synthesis of Catenanes from a BMP32C10-Based Cryptand Tuned by the Linkage Length of Paraquat Salts

AbstractA series of catenanes have been synthesized through olefin metathesis from a BMP32C10-based cryptand and paraquat guests attached with two terminal alkenes. Distribution of the catenane products can be significantly affected by the linkage length on the paraquat guests. In the presence of BMP32C10-based cryptand, the paraquat salt with a long linkage facilitates intramolecular olefin metathesis to release a [2]catenane as the sole catenation product, while the use of a paraquat salt with a shorter linkage leads to the simultaneous generation of [2]-, [3]-, and [4]-catenanes.

Stitching up the Belt[n]arenes

A synthetic strategy reported recently in the Journal of the American Chemical Society by Wang and coworkers, who used laser irradiation in the final key step of the synthesis, has led to the formation of highly strained belt[8]arene derivatives. This breakthrough could open doors to more controlled and precise syntheses of zigzag carbon nanotubes.

Hydrocarbon Belts with Truncated Cone Structures

We report in this communication the synthesis, structure, and application of a novel type of hydrocarbon belts. Starting from inexpensive and easily available resorcin[n]arenes, a closing-all-fjords strategy featuring exhaustive triflation of phenolic hydroxyl groups followed by consecutively the transition-metal-catalyzed vinylation and intramolecular olefin metathesis allowed facile construction of belt[n]arene[n]tropilidenes (n = 4, 6), which adopt double-stranded macrocyclic belt structures with unique truncated cone cavities. Selective hydrogenation reactions of olefin and benzene subunits led to diverse hydrocarbon belts with varied structures. Moreover, the resulting molecular belts acted as synthetic host materials to include selectively small molecules such as nitromethane and p-xylene.

Hydrocarbon‐stapled lipopeptides exhibit selective antimicrobial activity

Antimicrobial peptides (AMPs) occur widely in nature and have been studied for their therapeutic potential. AMPs are of interest due to the large number of possible chemical structural combinations using natural and unnatural amino acids, with varying effects on their biological activities. Using physicochemical properties from known naturally occurring amphipathic cationic AMPs, several hydrocarbon-stapled lipopeptides (HSLPs) were designed, synthesized, and tested for antimicrobial properties. Peptides were chemically modified by N-terminal acylation, C-terminal amidation, and some were hydrocarbon stapled by intramolecular olefin metathesis. The effects of peptide length, amphipathic character, and stapling on antimicrobial activity were tested against Escherichia coli, three species of Gram-positive bacteria (Staphylococcus aureus, Bacillus megaterium, and Enterococcus faecalis), and two strains of Candida albicans. Peptides were shown to disrupt liposomes of different phospholipid composition, as measured by leakage of a fluorescent compound from vesicles. Peptides with (S)-2-(4'-pentenyl)-alanine substituted for l-alanine in a reference peptide showed a marked increase in antimicrobial activity, hemolysis, and membrane disruption. Stapled peptides exhibited slightly higher antimicrobial potency; those with greatest hydrophobic character showed the greatest hemolysis and liposome leakage, but lower antimicrobial activity. The results support a model of HSLPs as membrane-disruptive AMPs with potent antimicrobial activity and relatively low hemolytic potential at biologically active peptide concentrations.

Donor/Acceptor-Stabilized 1-Silaketene: Reversible [2+2] Cycloaddition with Pyridine and Evolution by an Olefin Metathesis Reaction.

The reaction of silacyclopropylidene 1 with benzaldehyde generates a 1-silaketene complex 2 by a formal atomic silicon insertion into the C=O bond of the aldehyde. The highly reactive 1-silaketene 2 undergoes a reversible [2+2] cycloaddition with pyridine to give sila-β-lactam 3. Of particular interest, in the presence of 4-dimethylaminopyridine (DMAP), 1-silaketene complex 2 evolves through an intramolecular olefin metathesis reaction, generating a new 1-silaketene complex 8 and cis-stilbene. Theoretical studies suggest that the reaction proceeds through the formation of a transient silacyclobutanone, a four-membered-ring intermediate, similar to that proposed by Chauvin and co-workers for the transition-metal-based olefin metathesis.

Conformational Fixation of a Rectangular Antiaromatic [28]Hexaphyrin Using Rationally Installed Peripheral Straps.

A rectangular [28]hexaphyrin bearing outer straps at the long side has been synthesized by SN Ar reaction of [26]hexaphyrin with allyl alcohol, intramolecular olefin metathesis by using Hoveyda-Grubbs second-generation catalyst, and reduction with NaBH4 . The peripheral straps enforce a rectangular conformation for the [28]hexaphyrin, which shows Hückel antiaromatic character, as confirmed by its planar X-ray structure, a strong paratropic ring current, characteristic UV/Vis/NIR absorption features, small electrochemical HOMO-LUMO gap, and very fast S1 decay.

Intramolecular olefin metathesis as a robust tool to synthesize single-chain nanoparticles in a size-controlled manner

A comprehensive investigation of ruthenium-catalyzed intramolecular olefin metathesis was conducted for establishing a general approach to synthesize size-controlled SCNPs.

Synthesis of linear [5]catenanes via olefin metathesis dimerization of pseudorotaxanes composed of a [2]catenane and a secondary ammonium salt.

[5]Catenanes were synthesized by olefin metathesis dimerization. The reaction of pseudorotaxanes, which were derived from a [2]catenane and one equivalent of an ammonium salt bearing two terminal olefins in dichloromethane, with a catalytic amount of Grubbs catalyst afforded linear [5]catenanes in 12% yield. Intermolecular and intramolecular olefin metathesis reactions were controlled by the length of the alkyl chain of the ammonium salts.

Total synthesis of carbocyclic nucleoside (+)-neplanocin A

Asymmetric total synthesis of (+)-neplanocin A was concisely achieved from readily available d-galactose via the regioselective and diastereoselective amination of carbocyclic polybenzyl ether using chlorosulfonyl isocyanate and intramolecular olefin metathesis using second-generation Grubbs catalyst.

ChemInform Abstract: Total Synthesis of (‐)‐Englerin A.

AbstractThis new and novel total synthesis gives englerin A in 11% overall yield and includes an intramolecular olefin metathesis ring closure reaction and a highly stereoselective oxygen bridge formation as key steps.

Total synthesis of (−)-Englerin A

A novel and efficient total synthesis of Englerin A is reported. The synthesis featured an intramolecular olefin metathesis ring closure reaction and a highly stereoselective oxygen bridge formation induced by an iodonium ion. This strategy can be used for the synthesis of natural products Englerin A and Englerin B and can provide flexibility in the preparation of various 9-substituted analogues of Englerin A for further structure–activity relationship studies.

Total synthesis of (+)-valienamine and (−)-1-epi-valienamine via a highly diastereoselective allylic amination of cyclic polybenzyl ether using chlorosulfonyl isocyanate

The total synthesis of (+)-valienamine and (−)-1-epi-valienamine was concisely accomplished from readily available d-glucose via a highly diastereoselective amination of chiral benzylic ether using chlorosulfonyl isocyanate, intramolecular olefin metathesis, and diastereoselective reduction of cyclic enone using l-Selectride as the key steps.

Synthesis and Structural Revision of Phomopsin B, a Novel Polyketide Carrying a 10-Membered Cyclic-Ether Ring

Total synthesis of the proposed structure 2 for phomopsin B was achieved by using an intramolecular olefin metathesis as a key step. The spectral data, however, did not match with those of the natural product reported. Re-examination of the reported NMR data led to the structural revision of phomopsin B to known dothiorelone A 18. The R configuration of dothiorelone A was determined by total synthesis through a cross-metathesis with a chiral olefin 19.

Simple and efficient synthesis of highly functionalized cyclohexanes; formal total synthesis of ovalicin and fumagillin

Two chiral cyclohexanes 4 and 6, which are key intermediates for the total synthesis of ovalicin 1 and fumagillin 2, respectively, were synthesized from (2 R,3 S) 1,2-epoxy-4-penten-3-ol. The key steps involve an efficient construction of divinylalcohol 7 using methallyl Grignard reagent 9c, and an intramolecular olefin metathesis of 7.

Carbon−Carbon Bond Formation Involving a Vinylidene Ligand and Ferrocenyl Substituent in Cationic Ruthenium Complexes

A formal intramolecular olefin metathesis process between the C═C double bond of a vinylidene ligand and a pendant vinyl group in several ruthenium complexes, each with a ferrocenyl group, is followed by an additional intramolecular C−C bond formation between a Cp ligand of the ferrocenyl substituent and the vinylidene ligand. The regioselectivity of the C−C bond formation reaction at either the substituted or the nonsubstituted Cp group of the ferrocenyl group is possibly influenced by a steric effect between the neighboring substituent near the ferrocenyl group and the phosphine ligand on the ruthenium metal center. The structure of one ruthenium complex resulting from such a C−C bond formation has been fully characterized by a single-crystal X-ray diffraction analysis.

A Facile Synthesis of Lentiginosine Analogues Based on a Highly Regio‐ and Diastereoselective Allylic Amination Using Chlorosulfonyl Isocyanate

AbstractThe concise synthesis of the lentiginosine analogues pyrrolizidine alkaloid 2 and pyrroloazepine alkaloid 3 has been achieved from inexpensive and readily available D‐lyxose. The key steps in the synthesis included regio‐ and diastereoselective amination, inter‐ or intramolecular olefin metathesis, and Appel cyclization. The anti‐3,4‐amino alcohol 6, essential for the preparation of the title compounds 2 and 3, was synthesized by the regio‐ and diastereoselective amination of anti‐3,4‐tribenzyl ether 7 using chlorosulfonyl isocyanate. The reaction of 7 with chlorosulfonyl isocyanate in toluene at 0 °C afforded 6 exclusively with a diastereoselectivity of 26:1 in 84 % yield. These results can be explained by the neighboring‐group effect, which leads to retention of thestereochemistry.

Stepwise Synthesis and Selective Dimerisation of Bis‐ and Trisloop Tetra‐urea Calix[4]arenes

Tetra-urea calix[4]arenes substituted with four mono- or bisalkenyl residues have been converted into bis- or tetraloop compounds by intramolecular olefin metathesis, with use of a tetratosylurea calix[4]arene as template. The same strategy has now been used to synthesise trisloop compounds and bisloop compounds with adjacent loops, completing the series of the loop-containing tetra-urea derivatives. A tetra-urea calix[4]arene of the AABB type, where A stands for a bisalkenyl- and B for a monoalkenyl-substituted urea unit, was used as precursor for the three loops. It was easily synthesised from a tetraamino calix[4]arene in which two adjacent amino groups were Boc-protected. The ABCB-type precursor for the two adjacent loops was prepared through protection of two opposite amino functions with trityl groups. The capabilities of the novel macrocyclic tetra-ureas for the selective formation of hydrogen-bonded dimers were studied.

An Efficient Synthesis of Aminocyclopentitols via the Stereoselective Amination of Polybenzyl Ethers Using Chlorosulfonyl Isocyanate.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

An Efficient Synthesis of Aminocyclopentitols via the Stereoselective Amination of Polybenzyl Ethers Using Chlorosulfonyl Isocyanate

An efficient stereoselective route for the preparation of stereoisomeric aminocyclopentitols 3- 5 was achieved using a six-step sequence starting from the corresponding D-sugars. Key steps of the synthesis of the title compounds involved the regioselective and diastereoselective amination of cinnamylic 1,2- ANTI- or 1,2- SYN-tribenzyl ethers using chlorosulfonyl isocyanate (CSI), intramolecular olefin metathesis, and diastereoselective dihydroxylation.