Synthesis of a highly hydrophobic cyclic decapeptide by solid-phase synthesis of linear peptide and cyclization in solution

A general method was described to synthesize a highly hydrophobic cyclic peptide,cyclo[LWLWLWLWLQ]where underlines indicate D-configuration of the amino acid,by a two-step solid-phase/solution synthesis strategy.The linear decapeptide was assembled by standard Boc chemistry on solid-phase and subsequently cyclized in solution with high efficiency and reproducibility. In subsequent purification by semi-preparative HPLC,50%(v/v) DMF/H_2O was employed as the solvent to overcome the difficulty of solubilization...

Rhodium-catalyzed selective[2+2+2]cyclizations of 1,6-diynes with monoynes leading to isoindolines and isobenzofurans

A highly efficient and selective[2+2+2]cyclization of diynes and monoalkynes was catalyzed by rhodium under room temperature in water/THF mixed solvent,affording isoindolines and isobenzofurans in good to excellent yields.The center atoms (N,O) in the diynes showed a significant effect for the cyclization.

N-Radical enabled cyclization of 1,n-enynes

Compared to the widely used carbon-centered radicals,N-radicals have been relatively unexplored owing to the lack of practical and convenient production methods.Over the past few years,benefitting from the resurgence of reliable and controllable radical chemistry,N-radicals have been produced via thermal decomposition,oxidants,metal salts,or electrocatalysis.Therefore,numerous N-radical enabled cyclization of 1,n-enynes methods have been developed,providing a versatile and concise synthetic platform for the preparation of complex cyclic systems and natural products containing elaborate ring frameworks.In this review,we will summarize recent advances in the promising field of radical chemistry focusing on the production methods of N-radicals and their cyclization patterns,associated mechanisms,unmet challenges,and future opportunities.

The Mechanism on Cyclization, Debenzylation and Oxidation of 1-[1-(Benzyloxy)-3-methylnaphthalen-4-yloxy]propan-2-one

1-[1-（Benzyloxy）-3-methylnaphthalen-4-yloxy]propan-2-one （la） took place a cyclization, debenzylation and oxidation to form 9-substitued benzo[de]chromene-7,8-dione （2a） and 5-benzyl-9-substitued benzo[de]chromene-7,8-dione （3a）. The mechanisms for these reactions were discussed.

Stereoselective Functionalization at C-2 and C-3 of the Gibberellin via an Intramolecular Free Radical Cyclization Approach

Stereoselective functionalization at C-2 and C-3 of the gibberellin skeleton was achieved via an intramolecular free radical cyclization approach using a tethered C-19 halomethyl ester as the radical precursor.

Ferric Chloride Catalyzed Isomerization and Cyclization of Geraniol, Linalool and Nerol

Ferric chloride catalyzes the isomerization and cyclization of geraniol, linalool and nerol in acetonitrile giving a-terpineol in good to high yields.

Silver-catalyzed carboxylative cyclization of alkynic hydrazones with carbon dioxide

The development of new catalytic methodologies to synthesize heterocyclic fine chemicals using carbon dioxide as a synthon has attracted considerable attention. Herein, we report the silver( I)-catalyzed carboxylative cyclization of a variety of alkynic hydrazones with carbon dioxide to produce the corresponding 1,3,4-oxadiazin-2-ones under mild reaction conditions. In this reaction, silver(I) salts play a π-Lewis acid role for the highly efficient activation of the alkyne moiety in the hydrazone substrates. Single-crystal X-ray analysis and NOE experiments confirm that the newly formed oxadiazinone products exhibit Z configuration. Based on control experiments and NMR studies, a mechanism including the formation of a reactive carbazate intermediate, electrophilic cyclization, and subsequent protonation is proposed. This study offers an efficient and atom- economical method for the synthesis of biologically important 1,3,4-oxadiazin-2-ones.

Oxidative Cyclization of Azo-coupling Products of 3-Isopropenyltropoloneand 3-Cinnamoyltropolone with Bromine

new method to synthesize heterocycle-fused troponoid compounds by oxidizing azocoupling products of 3-isopropenyltropolone and 3-cinnamoyltropolone with bromine in the presence of pyridine was reported for the first time. Reaction of azo-couping products of 3-isopropenyl tropolone 1a similar to f and 3-cinnamoyltropolone 3a similar to d with excess bromine afforded heterocycle-fused troponoid compounds 2a similar to f, 4a similar to d, respectively.

Palladium-catalyzed Cascade Cyclization-Coupling Reaction of Benzyl Halides with N, N-Diallylbenzoylamide

A novel type of palladium-catalyzed cascade cyclization-coupling reaction has been found. Reaction of N, N-diallylbenzoylamide 1 with benzyl halides 2 afforded the corresponding dihydropyrroles 3 in moderate to excellent yields.

Cyclization and halogenation of substituted o-allylphenols with diacetoxyiodobenzene in the presence of iodine or bromine

Substituted 2-halomethyl-2,3-dihydrobenzofurans were synthesized in one pot and in mild yield from substituted o-allylphenols with diacetoxyiodobenzene in the presence of 12 or Br2 in dry CH2Cl2 under reflux.

Cyclization Reaction of α-Triazolyl-α, β-unsaturated Ketones with Phenyl hydrazine

The reaction of α-triazolyl-α, β-unsaturated ketones with phenyl hydrazine was studied. The result indicated that cyclization took place and new heterocyclic compounds of substituted 4,5-2H-pyrazoles were obtained, whose structures and conformation were characterized by 1H NMR, IR, MS, elemental analysis and X-ray diffraction.

β-Lactam Templated Macrocyclization:Synthesis of 12-Membered Macrolide

A novel macrolactonization method was developed using a chiral β-lactam as the template. This novel method features that the macrocyclization is simultaneously achieved while a TBS protected hydroxy group is deprotected.

STUDY ON THE INTRAMOLECULAR CYCLIZATION THROUGH OPENING OF EPOXIDE I CYCLIZATION OF N-METHYL-N-BENZOYLMETHYLENE-β-PHENYL-α,β-EPOXYPROPIONAMIDE IN APROTIC SOLVENT

Intramolecular cyclization of A catalyzed by IDA in benzene or THF yields two γ-lactams through C-alkylation and one δ-and one 7-membered lactam by O-alkylation.

An Efficient Cationic Cyclization Approach for the Construction of Labdane Diterpenoid Decalin Ring Skeleton

An effective approach for the construction of the decalin ring skeleton of labdane diterpenoids was developed based on a key biomimetic cationic polyene cyclization of an epoxy allylsilane precursor. The synthetic approach demonstrated here would be useful in the enantioselective and diastereoselective total synthesis of natural labdane diterpenoids in general.

Polymer-support Selenium-induced Electrophilic Cyclization:Solid-phase Synthesis of Flavonoids

The Lewis acid mediated polystyrene supported selenium cyclization of chalcones and oxidative cleavage of selenium resins flavonoids in good yields and purities have been reported. induced intramolecular gave the corresponding

Potassium Ferricyanide Oxidative Cyclizationof Arylaldehyde with o-Phenylenediamine and o-Aminophenol to 2-Arylbenzimidazoles and 2-Arylbenzoxazoles

Some new benzimidazoles and benzoxazoles have been prepared under mild condition by oxidative cyclization of arylaldehyde witho-phenylenediamine ando-aminophenol using potassium ferricyanide as oxidant

Study of Intramolecular Cyclization of N-styryl-oxo-cinnamides (Ⅱ)

The preparations and intramolecular cyclizations of amides 5, (N-methyl-N-(2 - trans-2-phenylethenyl)-3-phenyl-2, 3-cis-oxiranecarboxamide) and 8, (N-methyl-N-(2-cis-2-phenylethenyl ) - 3 -pheny 1-2, 3 - cis -oxiranecarboxamide) were reported.

Studies on the cyclization reaction of D-aspartic acid

The cyclization reaction of D-aspartic acid was studied, the carboxyl groups of D-aspartic acid were protected by benzyl alcohol to give compound D-dibenzyl aspartate. Then （4R）-benzyl azetidine-2-one-4-carboxylate and meso-3,6-disubstituted piperazine-2,5-diones were synthesized via intramolecular cyclization and intermolecular cycfization of D-dibenzyl aspartate, respectively, and their structures were confirmed by ^1 H NMR and MS. Both cyclization reaction conditions were also investigated in detail.

Construction of Spirooxindole Skeleton Through Intramolecular Dieckmann Cyclization

A highly efficient and direct approach was developed to construct the structurally diverse spirooxindole skeleton,which is an important basic motif in natural products.Both the 3,30-pyrrolidonyl spirooxindoles and spiroindolin-2-one dlactones were 2smoothly obtained by the intramolecular Dieckmann cyclization of oxindoles in excellent yield under mild conditions.

CARBONIUM CYCLIZATION--STUDIES ON LIGNANS CONTAINING THE DIBENZOCYCLOOCTADIENE SYSTEM.Ⅱ

The major products of carbonium cyclization of 1 are 2 and 3;2 is unstable and undergoes aerial oxidation to give 4.A similar product(6)from 5 is somehow stabilized by the extra ben- zoyloxy group(or OH)and can be stored without deterioration.