β-lactams from esters and silylimines: A revaluation. Synthesis of N-unsubstituted 4-alkyl-β-lactams

The first preparation of enolizable silylimines is reported. The “in situ” trapping of these species with lithium enolates of esters gives rise in fairly good yields to N-unsubstituted 4-alkyl-β-lactams.     

Synthesis of α-pyrones from α-oxo ketene dithioacetals

α-Oxo ketene dithioacetals can be converted into α-pyrones in a three step process involving 1,2-nucleophilic addition of ester or ketone enolate anions, acid promoted rearrangement, and subsequent enol lactonization. Utilization of ester enolates affords 6-alkylthio α-pyrones while ketone enolates give 3-alkyl substituted α-pyrones.     

Synthesis of keto acids from olefins andω-chloroformyl carboxylic esters

Summary The following were synthesized for the first time by the catalytic method from the corresponding alkene and acid chloride; 1) 6-oxo-7-decenoic acid; 2) 8-methyl-6-oxo-7-nonenoic acid; 3) 4-oxodecanoic acid; 4) 6-oxododecanoic acid; 5) 7,7,8-trimethyl-6-oxo-8-nonenoic acid; 6) 7,7,8-trimethyl-6-oxononanoic acid; 7) 6-oxotridecanoic acid (this acid was prepared previously by organomagnesium synthesis [4]).     

Synthesis of β-keto esters in-flow and rapid access to substituted pyrimidines

We have developed an in-flow process for the synthesis of β-keto esters via the BF(3)·OEt(2)-catalyzed formal C-H insertion of ethyl diazoacetate into aldehydes. The β-keto esters were then condensed with a range of amidines to give a variety of 2,6-substituted pyrimidin-4-ols.     

Synthesis of β-carbolines from aldehydes and ketones via the α-siloxy α,β-unsaturated esters

We report an efficient method for the synthesis of β-carbolines from α-siloxy α,β-unsaturated esters, which are accessible from a variety of aldehydes and ketones.     

Synthesis of β-Lactams from Acids and Imines Using Thiocarbonyldiimidazole

Thiocarbonyldiimidazole has been found to be an efficient acid activator for the synthesis of β-lactams by ketene-imine cycloaddition at room temperature. The experimental procedure is simple and results in excellent yields of the products. All products were characterized by spectral data and elemental analyses.     

Synthesis of β3-amino acid and peptides from D-ribose

Synthesis of new β³-amino acid, peptides and conformational analysis are reported from d-ribose, using Wittig olefination and Aza-Michael addition.     

Synthesis of Isoquinoline Derivatives from β-Hydroxyarylethanamides

A simple and efficient protocol for the construction of medicinally important substituted isoquinolines through intramolecular cyclization of β-hydroxyarylethanamides using acetic anhydride and phosphorous pentoxide in dioxane has been described. The chemo- and regioselectivities due to the influence of different catalysts were investigated and optimized for good to excellent yields. All the synthesized compounds have been characterized by NMR and mass spectral analyses.     

ZrCl4-Catalyzed Synthesis of β-Aminosulfides from Aziridines and Thiols

A simple and efficient synthesis of β-aminosulfides has been introduced by ring opening of aziridine rings with aromatic thiols in the presence of zirconium(IV) chloride under solvent-free conditions at room temperature.     

Synthesis of 1,3-Dioxolane Derivatives from β-Chlorolactic Acid and Ketones

2-Ethyl-2-methyl-5-methylene-1,3-dioxolan-4-one and 5-methylene-2,2-pentamethylene-1,3-dioxolan-4-one were synthesized by reaction of -chlorolactic acid with methyl ethyl ketone and cyclohexanone, respectively, followed by dehydrochlorination of intermediate 5-chloromethyl derivatives.     

Synthesis of α,α-disubstituted α-amino esters: nucleophilic addition to iminium salts generated from amino ketene silyl acetals

Alkoxycarbonyl iminium species are prepared easily by the oxidation of tetrasubstituted amino ketene silyl acetals, and subsequent nucleophilic addition of Grignard reagents to the iminium salts gives α,α-disubstituted α-amino ester derivatives in moderate to good yields, in which aryl and ethynyl substituents are readily introduced.     

Improved Synthesis of Icaritin and Total Synthesis of β-Anhydroicaritin

Natural products icaritin and β-anhydroicaritin with P-glycoprotein(P-gp) inhibitory activities were ciently synthesized in nine steps from commercially available phloroglucinol. A modified Algar-Flynn-Oyamada cyclization and relay Claisen-Cope rearrangement were employed in this concise route. Oiir synthesis offers opportunities to synthesize various icariin analogues for biological and pharmacological investigations.     

Synthesis of novel isoxazoline-fused cyclic β-amino esters by regio- and stereo-selective 1,3-dipolar cycloaddition

Isoxazoline-fused 2-aminocyclopentanecarboxylate derivatives were regio- and stereo-selectively synthesized by nitrile oxide 1,3-dipolar cycloaddition to cis- or trans-ethyl-2-aminocyclopent-3-enecarboxylates. The compounds were prepared in enantiomerically pure form by enzymatic resolution of the racemic bicyclic β-lactam.     

Isolation and characterization of four novel β-Sitosteryl esters from Salvadora persica Linn.

Salvadora persica is virtuous to have a variety of phytoconstituents responsible for many biological activities some of them identified particularly while some are still to be acknowledged. A number of steroidal, glycosidic, terpenoids, saponins and functional esters are reported till date. The present study deals with extraction, isolation, and characterisation of four novel steroidal esters by systematic cold extraction of S. persica. The extracted phytoconstituents were characterised by sophisticated spectral UV, IR, NMR and MS, techniques. The reported four new β-Sitosteryl esters SP-2, 3, 5 and 6 were extracted and reported for the first time.     

Synthesis of 1,3-thiazoline derivatives from β-dicarbonyl compounds and phenacyl thiocyanate

Acetylacetone and ethyl acetoacetate undergo addition at the CN bond of phenacyl thiocyanate in the presence of Ni(acac)₂ to give the respective keteneN, S-acetals, which undergo smooth cyclization to afford 2-methylene-4-phenyl-1, 3-thiazoline derivatives when refluxed in THF.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1938–1940, November, 1993     

Synthesis of Terpenoid-Like Bischalcones from α- and β-Ionones and Their Biological Activities

Ionone-based terpenoid-like bischalcones (3a–h and 4a–h) were synthesized from the reaction of α- and/or β-ionones with aldehyde derivatives in excellent yields. The antibacterial activities of synthesized compounds were screened against human pathogenic micro-organisms by employing the disk-diffusion technique.     

Synthesis of β-d-glucopyranosyl- and β-d-galactopyranosylamines from 4-bromo-3-methylaniline and 2-amino-5-bromopyridine

The possibility of coupling of d-glucose and d-galactose with 4-bromo-3-methylaniline, 2,4,6-tribromoaniline, and 2-amino-5-bromopyridine was studied. The substituent in the aromatic ring was found to influence the conditions and possibility of the reaction. The yields of β-d-glucopyranosyl- and β-d-galactopyranosylamines from 4-bromo-3-methylaniline and 2-amino-5-bromopyridine were 50–65%; 2,4,6-tribromoaniline did not react at all.     

Synthesis of esters of α-vinyloxyethylcarbamodithioic acid

Mono and diesters of 2-vinyloxyethylcarbamodithioic acid were synthesized by the reaction of (1-p-nitrophenyl)-2-vinyloxyethylaminoethanol with carbon disulfide. 3-[2-(Vinyloxyethyl)]-5-(4-nitrophenyl)-1,3-thiazolidine-2-thione was prepared and its structure was proved by X-ray diffraction analysis.