Stereoselective synthesis of advanced intermediates en route to Taxuspine U and X: a study of macrocyclization via ring closing metathesis to highly constrained twelve-membered rings

The stereoselective synthesis of an advanced intermediate of Taxuspine U and X has been accomplished using a ring closing metathesis strategy. The feasibility of ring closing metathesis in synthesizing highly constrained and functionalized macrocycles has been demonstrated provided the appropriate substrate structure and substitution pattern are chosen.     

Stereoselective synthesis of tarchonanthuslactone via the Prins cyclisation

The stereoselective total synthesis of tarchonanthuslactone, a polyketide natural product, has been achieved. The synthesis exploits the high stereochemical control in the Prins cyclisation along with ring closing metathesis (RCM) as a key step.     

Total synthesis of heliannuol B, an allelochemical from Helianthus annuus

A total synthesis of the allelochemical heliannuol B 1 is described employing ring closing metathesis to generate the central benzoxepane ring system.     

Total synthesis of topsentolide B2

A stereoselective total synthesis of topsentolide B₂, a selective cytotoxic oxylipin against SK-OV-3 and SK-MEL-2 cancer cell lines has been achieved based on asymmetric dihydroxylation, Roush allylation, and ring closing metathesis (RCM) reactions. The synthesis is completed in 11 steps and 2.1% overall yield.     

A concise synthesis of β-lactam-sulfonamide hybrids

Using ring closing metathesis (RCM) as the key operation, a rapid access to β-lactams fused to a sultam moiety of variable ring size was developed from low cost, commercially available starting materials. An efficient RCM of 4-vinyl-azetidin-2-ones to give 1-aza-bicyclo[4.2.0]oct-4-en-8-ones is also reported.     

Efficient synthesis of 18-40 membered macrocyclic polyoxadiamides and polyoxatetraamides via ring closing metathesis

Ring closing metathesis of the appropriate 1,ω-dienes led to efficient synthetic approaches towards the corresponding macrocyclic polyoxadiamides and tetraamides with 18-40 membered ring sizes in good to excellent yields using Grubbs' catalyst.     

Stereoselective total synthesis of xyolide

A stereoselective total synthesis of xyolide is described employing MacMillan α-hydroxylation, Steglich esterification, and ring closing metathesis as key steps. The use of organocatalytic MacMillan α-hydroxylation to construct two of the chiral centers of the xyolide makes this approach attractive.     

Enantiospecific total synthesis of the putative structure of cryptopyranmoscatone B2

Total synthesis of THP tethered pyrone containing natural product cryptopyranmoscatone B2 was accomplished from commercially available 2-deoxyribose. The key THP unit was assembled by FeCl₃ catalyzed cyclization of an allyl alcohol. Brown allylation and RCM reactions were employed to construct the lactone unit. The synthesis represents the first total synthesis of the putative structure of the natural product.     

A stereoselective synthesis of (R)-5-hydroxy-3-(4-methoxyphenethyl)cyclohex-2-enone,towards total synthesis of Prelunularin

A first chiral strategy for synthesis of (R)-5-hydroxy-3-(4-methoxyphenethyl) cyclohex-2-enone reported. Key transformation includes Barbier allylation, ionic hydrogenation, Jeffery reaction, Katsuki Sharpless asymmetric epoxidation, reductive opening of epoxide and ring closing metathesis.     

A New Synthesis of Benzofurans from Phenols via Claisen Rearrangement and Ring‐Closing Metathesis

Based on Claisen rearrangement, the double bond isomerization of O‐allyl function together with the formation of O‐vinyl function in one pot, and ring‐closing metathesis (RCM), various phenols were transformed into various benzofurans in good yields.     

Synthesis, crystal structure and thermal behavior of dimethylgold(III) derivatives of salicylaldimine Schiff bases - Novel precursors for gold MOCVD applications

Dimethylgold(III) complexes with salicylaldimine Schiff bases of general formula Me₂Au(SalN-R) (R = methyl (1), iso-propyl (2), or cyclohexyl (3)) have been synthesized in a single step reaction from dimethylgold(III) iodide [Me₂AuI]₂ and N-substituted salicylaldimines. Single-crystal X-ray studies provide evidence of mononuclear four-coordinated complexes with square-planar coordination geometry. The temperature dependences of saturated vapour pressure of complexes have been studied by the Knudsen effusion method with mass spectrometric analysis of the composition of the gas phase. The thermodynamic parameters of the sublimation process ΔH^o_T and ΔS^o_T have been calculated. Thermal decomposition of the vapour of compounds has been studied by means of high temperature mass spectrometry in a vacuum, and by-products have been determined. All of these complexes show good volatility and thermal stability. For complex 2, which is more volatile and low-melting, pulse MOCVD experiments have been carried out at substrate temperatures lower than 200 °C. The deposited gold nanoparticles (5-15 nm) have been investigated by means of SEM and AFM.     

Studies towards the total synthesis of Sch 56036; isoquinolinone synthesis and the synthesis of phenanthrenes

The isoquinolinone hemisphere of Sch 56036 has been prepared using a modified Pomeranz-Fritsch reaction and the synthesis of the phenanthrene core has been modelled via a Suzuki coupling and subsequent ring closing metathesis.     

A short stereoselective synthesis of (+)-boronolide

A short and stereoselective synthesis of (+)-boronolide via oxidative functionalization of an olefin using a pendant sulfinyl group is described. Diastereoselective allylation was performed using Keck’s protocol and the lactone moiety was prepared by ring closing metathesis.     

Synthesis of pyranonaphthoquinone antibiotics involving the ring closing metathesis of a vinyl ether

The synthesis of two antibiotic pyranonaphthoquinones was performed by a straightforward synthetic route utilizing ring closing metathesis. Vinylation of 3-(1-propenyl)-2-hydroxymethyl-1,4-dimethoxynaphthalene under iridium catalysis and subsequent ring closing metathesis of 3-(1-propenyl)-2-vinyloxymethyl-1,4-dimethoxynaphthalene with Grubbs' catalyst paved the way to the natural antibiotics pentalongin and psychorubrin.     

The stereoselective total synthesis of PF1163A

A stereoselective total synthesis of 13-membered macrocycle PF1163A, an antifungal agent, has been accomplished for the first time starting from d-xylose. This approach involves a diastereoselective allylation of lactal ether,^3a reductive ring opening of tetrahydrofuran ring,^3b asymmetric methylation reaction, Yamaguchi esterification, and ring closing metathesis as key steps.     

RCM as a tool to freeze conformation of monosaccharides: synthesis of a β-mannopyranoside mimic adopting a conformation close to the biologically relevant B2,5 boat

The synthesis of a β-d-mannopyranoside analog, fully identical to the naturally occurring d-mannopyranose in terms of hydroxyl pattern, and displaying a skew-boat conformation close to a B_2,5 boat strongly believed to be adopted by the oxycarbenium transition state during glycosidic bond cleavage of β-mannane by family 26 β-mannanase, is described. The conformationally locked analog has been obtained by tethering the C-2 and C-5 carbon atoms of the sugar ring with a three carbon bridge using RCM methodology. Conformation of the mannose analog has been confirmed by NMR and molecular modelling.     

A Morita-Baylis-Hillman adduct allows the diastereoselective synthesis of styryl lactones

We disclosed herein a diastereoselective approach for the total syntheses of (±)-Leiocarpin A and (±)-Goniodiol. These biologically active styryl lactones were obtained from a common intermediate, prepared in five steps and 40% overall yield, using a simple synthetic sequence starting from a Morita-Baylis-Hillman adduct. The total syntheses of these styryl lactones were accomplished in nine steps. This is the first report on the total synthesis of this class of natural products starting from Morita-Baylis-Hillman adduct.     

Synthetic studies toward tricyclic cembranoids: a modular approach for the construction of the tricyclic framework of eunicin

The synthesis of a sugar derived allene and its intramolecular silver mediated etherification followed by ring closing metathesis has been explored for building the tricyclic framework of eunicin.     

Synthetic studies toward macrocidins: an RCM approach for the construction of the central cyclic core

The central macrocyclic core of the macrocidins was constructed using RCM as the key reaction. A preliminary investigation dealing with the key reactions, that is, the Dieckmann cyclization and the RCM, revealed that RCM of the β-ketoamide is better than RCM of the corresponding acyltetramic acid.     

Synthesis and Evaluation of the Cytotoxicities of Neoflavenes

The synthesis of neoflavene and neoflavenes with methoxy substituents at different positions are described. As starting materials, various salicylaldehydes were run through sequential reactions such as O‐allylation, Grignard reaction, oxidation, Wittig reaction, and ring‐closing metathesis to yield the target neoflavenes in good yield. Among the prepared neoflavenes, 7‐methoxy‐4′‐methoxyneoflavene ( 6e ) and 8‐methoxy‐4′‐methoxyneoflavene ( 6f ) exhibiting potential cell toxicities against various cells were disclosed. In particular, 6f which exhibited an IC₅₀ value of 6.5 ± 2.0 and 5.1 ± 1.1 μM against gastric carcinoma and lung carcinoma cells in vitro was found, respectively. Meanwhile, the structure and activity relationship of our synthesized neoflavenes is further discussed briefly.