Synthesis of three new Schizandrin Analogues

Schizandrin,isolatedfromSchisandrachinensisBaill,isadibenzocyclooctadienetypelignanwithvariousbiologicalactivitiesl.Niuandco-workershavestudiedthepharmacologicaleffectsofthiscompound'onthecentralnervoussystem.Theresults2showthatschizandrinpossessesextensive,significantanti-convulsiveactivities,particularlyregardingcerebraIprotectionandadjustmentofthecerebralcortexexcitementinhibitionprocess.Therefore,researchonthechemicalsynthesisofschzandrinanditsanaloguesisveryimportant.InourattCmPtCdtota…     

Synthesis and cycloaddition reactions of α-substituted acrolein dimethylhydrazones containing an acetal group

A series of new -substituted acrolein dimethylhydrazones containing an acetal group were synthesized. These hydrazones react with acrylonitrile or methyl acrylate according to the Diels—Alder reaction pattern to give substituted tetrahydropyridines. An unusual [2+4]- and [2+3]-cycloaddition cascade reaction involving -diethoxymethylacrolein dimethylhydrazone was discovered.     

Synthesis of new nanocopolymer containing β-lactams

Several new monocyclic β-lactam monomers bearing the NO₂ group 2a–g were synthesized via a [2 + 2] ketene–imine cycloaddition reaction (Staudinger reaction). Calculation of coupling constant of H-3 and H-4, and the X-ray crystallography of β-lactam 2e confirmed the cis stereochemistry of these β-lactams. Then aminophenyl β-lactams were synthesized by the reduction of NO₂ to NH₂ group in the presence of Raney Ni and hydrazine hydrate. Treatment of these aminophenyl β-lactams with acryloyl chloride and sodium bicarbonate (NaHCO₃), afforded the monomers bearing the NHCOCH=CH₂ group. These acrylated β-lactam monomers were dissolved in a warm mixture of butyl acrylate and styrene and then were converted to the corresponding polyacrylate nano β-lactams by emulsion polymerization in water. A unique feature of this methodology is the ability to incorporate water-insoluble compounds directly into the nanoparticle framework. Structures of the synthesized compounds were confirmed by physical and spectral analyses. Dynamic light scattering analysis and transmission electron microscopy of the final emulsions show that the nanoparticles were about 50–70 nm in diameter.     

Synthesis of α-aminonitriles under mild catalytic,metal-free conditions

α-Aminonitriles have been synthesized by a Strecker synthesis from aldehydes and ketones under mild catalytic, metal-free conditions. Aromatic aldehydes (1 equiv) were reacted with aromatic and 1° or 2° aliphatic amines (1 equiv) in EtOH containing 3 mol % of NH₄Cl to give high yields of α-aminonitriles. An alternative to adding NH₄Cl as a catalyst involved the use of excess TMSCN (1 equiv) and to promote the process. The reaction was also successful under microwave conditions using excess TMSCN with no solvent. Ketones similarly reacted with aromatic amines and excess TMSCN under conventional and microwave heating, but 30 mol % of added NH₄Cl was required for optimum conversion.     

Expeditious and efficient synthesis of Strecker’s α-aminonitriles catalyzed by sulfated polyborate

A straightforward, mild, efficient, and environmentally benign protocol for a three-component Strecker reaction of aldehydes or ketones, amines, and trimethylsilyl cyanide catalyzed by sulfated polyborate has been described to afford α-aminonitriles under solvent-free reaction conditions. The major advantages of the present method are excellent yields, shorter reaction time, simple experimental procedure, easy workup procedure, recyclability of the catalyst, solvent-free reaction conditions and ability to tolerate a variety of functional groups which gives economical as well as ecological rewards.     

Synthesis of novel α-acyloxycarboxamides containing vinylbis(silanes) through three-component Passerini reactions

A three-component efficient procedure is described for the synthesis of novel α-acyloxycarboxamides containing bis(trimethylsilyl)ethenyl group from 4-[2,2-bis(trimethylsilyl)ethenyl]benzaldehyde, aromatic carboxylic acids and isocyanides, via the Passerini reaction. This reaction proceeds smoothly and cleanly under mild conditions in H₂O and [bmim]BF₄ at room temperature and led to products in good yields. The silylated aldehyde was obtained via Peterson olefination reaction of terephthalaldehyde with tris(trimethylsilyl)methyllithium in THF at 0 °C.     

Synthesis of new α-hydroxyphosphonates and α-acetoxyphosphonates

A series of new α-hydroxyphosphonate (5–14) have been synthesized in high yields by reaction of β-chloro-α,β-unsaturated aldehydes (1–4) and trialkyl phosphite in the presence of chlorotrimethylsilane at room temperature under solvent-free conditions. In addition, compounds (5–14) were reacted with acetic anhydride in DBU to give the new α-acetoxyphosphonate derivatives (15–23). All these phosphonates (5–23) were obtained as mixtures of two (E and Z) isomers and fully characterized by multinuclear (¹H, ¹³C, and ³¹P) NMR, IR spectroscopy and HRMS.     

Synthesis and anion-exchange reactions of a new anionic clay, α-magnesium hydroxide

A new anionic clay, α-magnesium hydroxide, was synthesized by hydrolysis of magnesium acetate in propylene glycol. The structure of this α-hydroxide is similar to that of hydrotalcites. It consists of positively charged magnesium hydroxide layers arising out of partial protonation of the hydroxyl groups of the [Mg(OH)(2)] layers and loosely held anions in the interlayer region. As expected it ages readily in water to give β-magnesium hydroxide, brucite. While anion-exchange reactions of α-magnesium hydroxide could not be carried out in aqueous medium a number of anion-exchange reactions could be carried out successfully in ethanol medium.     

One-pot three component α-aminoalkylation of conjugated nitroalkenes and nitrodienes

Nitroethylenes possessing aryl, heteroaryl, and alkyl substituents at the β-position as well as δ-substituted nitrobutadienes undergo facile aminoalkylation at the α-position upon treatment with formaldehyde and a secondary amine in the presence of imidazole and trifluoroacetic acid to afford α-aminoalkylated nitroalkenes and nitrodienes in good to excellent yield and stereoselectivity.     

Synthesis of a benzoxazine monomer containing maleimide and allyloxy groups

A novel benzoxazine monomer 3-（4-allyloxy）phenyl-3,4-dihydro-2H-6-（N-maleimido）-l,3-benzoxazine （AMB） was synthesized and structure was confirmed by FT-IR, 1H NMR. Thermal analysis （DSC） of AMB showed the introduction of allyloxy group melting point and exhibited a narrow and symmetric curing exothermic window.     

Synthesis of new liquid crystalline compounds containing an α,β-unsaturated ketone and β-chloroketone groups in the side chain

A number of new liquid crystalline compounds containing an ,-unsaturated ketone or -chloro ketone moiety in the side chain were synthesized. The key intermediates in the synthesis were 1-(4-hydroxy-phenyl)-2-octen-1-one and 3-chloro-1-(4-hydroxyphenyl)octan-1-one which were prepared from 5-(4-hydroxy-phenyl)-3-pentyl-4,5-dihydroisoxazole and 3-hydroxy-1-(4-hydroxyphenyl)octan-1-one, respectively.Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 10, 2004, pp. 1526–1531.Original Russian Text Copyright © 2004 by V. Kovganko, N. Kovganko, Bezborodov.     

One-stage synthesis of adamantyl-containing α-aminonitriles

Reactions of 2-adamantan-2-one, acetone cyanohydrin, and amine lead to the formation of substituted 2-amino-2-cyanoadamantanes. The reaction is of a general character as has been proved by examples on a series of ketones and amines and it proceeds through the formation from the acetone cyanohydrin and amines of 2-amino-2-cyanopropane derivatives reacting further with the carbonyl compounds.     

Asymmetric synthesis of β,β-difluoroamino acids via cross-coupling and Strecker reactions

β,β-Difluoroamino acids were synthesized from commercially available ethyl bromodifluoroacetate using cross-coupling and Strecker reactions as key steps. The coupling reaction of aryl iodides with ethyl bromodifluoroacetate gave the corresponding coupling products, which were transformed to 2-difluoromethyl-1,3-oxazolidines in two steps. Boron trifluoride etherate promoted Strecker reaction of 2-difluoromethyl-1,3-oxazolidines gave α-amino nitriles in good yields and diastereoselectivities. After removal of chiral auxiliary and hydrolysis of the nitrile group, β,β-difluorophenylalanine was obtained with 73% ee. Partial racemization occurred during the hydrolysis of nitrile group.     

Some α-amino acids containing trifluoromethyl groups

Summary Ethanolamine was added to , -ditrifluoromethylacrylic ester and hexafluorovaline ester was hydroxyethylated. Both reactions yielded the ester of N-(-hydroxyethyl)-hexafluorovaline, which could be used as the starting material for the synthesis of physiologically active substances.     

Stereoselective Synthesis of α-L-Rhamnopyranosyl Phosphonates via α-L-Rhamnopyranosyl Trifluoroacetate

α-L-Rhamnopyranosyl phosphates 8a-b～12a-b were obtained in high yield and high stereoselectivity from α-L-rhamnopyranosyl trifluoroacetate 2a-b and phosphoric acid diesters in the presence of a Lewis acid.     

Synthesis of glycosyl disulfides containing an α-glycosidic linkage

A wide range of symmetrical and unsymmetrical glycosyl disulfides is synthesized with focus on the use of α-glycosyl thiols. Oxidation of α-glycosyl thiols with iodine leads to symmetrical α,α-glycosyl disulfides, while unsymmetrical disulfides are readily synthesized from α- and β-glycosyl thiols under the action of DDQ. Thus, glycosyl disulfides containing at least one α-glycosidic linkage are made available.     

Synthesis and reactions of α-fluoro-α-amino amides

N-((S)-1-Phenylethyl)halofluoroethanamides have been investigated as precursors to N-protected α-fluoro-α-amino amides by nucleophilic displacement of halide with nitrogen nucleophiles such as potassium phthalimide, sodium succinimide, sodium glutarimide, trimethylamine and sodium azide. With single diastereoisomers of the iodofluoroethanamide, clean inversion of configuration occurs at room temperature, but subsequent epimerisation may occur as a result of the liberated iodide. The α-fluoro-α-amino amides made underwent a wide variety of reactions depending on conditions, but in many cases the carbon-fluorine bond was compromised. However, reacting trimethylamine and N-((S)-1-phenylethyl)iodofluoroethanamide gave the corresponding α-fluorobetaine amide, and subsequent acidic hydrolysis led to α-fluorobetaine as the first example of an ‘unprotected’ α-fluoroamino acid.     

Synthesis of leucine-enkephalin analogs containing α-amino squaric acid

Novel Leu-enkephalin analogs 10a-c in which the Tyr¹, Gly², or Gly³ residue of Leu-enkephalin 9 was replaced with α-amino squaric acid analog Sq-Tyr 8b or Sq-Gly 8a were synthesized starting from 14 or 18. Conformational analysis of 10a-c together with its model compound 26 and their opioid receptor binding activity were evaluated.     

Solvent-free synthesis of substituted thiopyrans via multicomponent reactions of α-haloketones

A straightforward and efficient method for the synthesis of thiopyran derivatives via three-component reaction of alkyl propiolate, benzoylisothiocyanate or its derivatives and α-haloketones in the presence of triphenylphosphine under solvent-free conditions at 70℃ without using any catalyst is reported, The method offers several advantages including high yields of products and an easy work-up procedure.     

Asymmetric Strecker synthesis of α-arylglycines

A practically simple three-component Strecker reaction for the asymmetric synthesis of enantiopure α-arylglycines has been developed. Addition of a range of aryl-aldehydes to a solution of sodium cyanide and (S)-1-(4-methoxyphenyl)ethylamine affords highly crystalline (S,S)-α-aminonitriles that are easily obtained in diastereomerically pure form. Heating the resultant (S,S)-α-aminonitriles in 6 M aqueous HCl at reflux resulted in cleavage of their chiral auxiliary fragments and concomitant hydrolysis of their nitrile groups to afford enantiopure (S)-α-arylglycines. The enantiopurities of these (S)-α-arylglycines were determined via derivatization of their corresponding methyl esters with 2-formylphenylboronic acid and (S)-BINOL, followed by (1)H NMR spectroscopic analysis of the resultant mixtures of diastereomeric iminoboronate esters.