A one step synthesis of ω-hydroxyacetylenic carboxylic acids

A convenient chemioseLective method to prepare ω-hydroxyacetylenic carboxylic acids from unprotected ω-alkyn-1 ols and ω-bromo acids is described.     

Stereoselective,nonracemic synthesis of ω-borono-α-amino acids

ω-Unsaturated α-amino acids are synthesized through condensation of allyl and propargyl bromides or of 9-bromoundecene with a Ni(II) complex of the Schiff base derived from glycine and BPB. Hydroboration with Ipc₂BH followed by oxidation with acetaldehyde affords enantiomerically pure ω-borono-α-aminocarboxylic acids.     

Direct synthesis of α-thio aromatic acids from aromatic amino acids

Modified amino acids are useful synthetic components in both chemistry and biology. Here we describe a simple, scalable two-step procedure to generate α-thio aromatic acids from aromatic amino acids with yields of up to 96%. Diazotization and α-lactone mediated bromination efficiently form the α-bromo acid with retention of configuration. Thiol substitution with mild reagents such as sodium hydrosulfide or sodium trithiocarbonate provides the inverted, free α-thio acid. The mildly acidic soft nucleophile can then be utilized in many synthetic applications.     

Copper-mediated synthesis of N,N''''-diarylhydrazines from boronic acids

N,N0-Diarylhydrazines have been prepared via the reaction of N-Boc-aryl hydrazines with boronic acids mediated by copper acetate. This mild reaction condition tolerates the presence of a variety of functional groups.     

Electrochemical synthesis of 1,2-disilylethanes from α-silylacetic acids

The synthesis of 1,2-disilylethanes [R(1)R(2)R(3)Si(CH(2))(2)SiR(1)R(2)R(3)] is usually conducted by using noble metal reagents or catalysts. This work describes a new electrochemical synthetic method for their preparation in good yields by oxidation of α-silylacetic acids at Pt anodes (Kolbe electrolysis). Most of the reported synthesized 1,2-disilylethanes in this work are unknown.     

Facile synthesis of α-hydroxy carboxylic acids from the corresponding α-amino acids

An effective and improved procedure is developed for the synthesis of α-hydroxy carboxylic acids by treatment of the corresponding protonated α-amino acid with tert-butyl nitrite in 1,4-dioxane–water. The amino moiety must be protonated and located α to a carboxylic acid function in order to undergo initial diazotization and successive hydroxylation, since neither β-amino acids nor acid derivatives such as esters and amides undergo hydroxylations. The method is successfully applied for the synthesis of 18 proteinogenic amino acids.     

Microwave-assisted synthesis of dialkyl ω-azidoalkylphosphonates

An efficient and reproducible microwave-assisted synthesis of dialkyl ω-azidoalkylphosphonates via nucleophilic substitution of the appropriate dialkyl ω-bromoalkylphosphonates by sodium azide in water or dimethylformamide (DMF) as solvent has been developed. This process has been optimized for batch reactors. The target, structurally diverse dialkyl ω-azidoalkylphosphonates with different steric hindrance around the phosphonato groups and containing unbranched side carbon chains of different lengths (n?=?2–6), has been obtained in moderate to high yields (39–87%).     

General method of synthesizing esters of ω-nitropolyenic acids

Summary A general method has been developed for the synthesis of esters of polyenic -nitro acids.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya No. 11, pp. 2093–2095, November, 1964     

Copper-mediated synthesis of N,N′-diarylhydrazines from boronic acids

N,N＇-Diarylhydrazines have been prepared via the reaction of N-Boc-aryl hydrazines with boronic acids mediated by copper acetate. This mild reaction condition tolerates the presence of a variety of functional groups.     

Stereocontrolled synthesis of D-α-hydroxy carboxylic acid from L-amino acids

Optically active D-α-hydroxy carboxylic acids are obtained from L-amino acids via L-α-halocarboxylic acids and their stereoselective reaction with cesium p-nitrobenzoate.     

A stereoselective synthesis of the allo-bile acids from the 5β-isomers

The allo-bile acids are a subset of the family of steroidal detergents found in most vertebrates. Because there are no major biological feedstocks for isolation of the allo-bile acids, they must be synthesized from the abundant 5β-reduced isomers. Here we report a general set of methods for the synthesis of allo-bile acids from the corresponding 5-β isomers demarcated by a selective C-3 oxidation, IBX unsaturation, and stereoselective saturation.     

On the synthesis of ω-appended hypericin derivatives

Summary A method for the preparation ofbis--appended hypericin derivatives bearingn-octyl,n-hexadecyl, and 2-(2-(2-hydroxyethoxy)-ethoxy)-ethoxymethyl substituents was developed. The key step — the synthesis of appropriately -substituted emodin derivatives — was achieved by solvolyzing 3-bromomethyl-1,6,8-triacetyloxy-anthracene-9,10-dione (-bromo triacetylemodin) in an appropriate alcohol in the presence of silver perchlorate. The correspondingbis--substituted hypericins were then prepared conventionally by dimerizing the -substituted emodin anthrones. The latter were prepared by reduction of the -appended emodins.

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Zur Synthese von -substituierten Hypericinderivaten

Zusammenfassung Eine Methode zur Darstellung vonbis--substituierten Hypericinderivaten wurde entwickelt. Der Schlüsselschritt — die Synthese der entsprechenden Emodinderivate — wurde durch die Solvolyse von 3-Bromomethyl-1,6,8-triacetyloxyanthracen-9,10-dion (-Bromtriacetylemodin) im entsprechenden Alkohol in Gegenwart von Silberperchlorat ermöglicht. Die entsprechendenbis--substituierten Hypericinderivate wurden auf konventionelle Weise durch Dimerisierung der -substituierten Emodinanthrone dargestellt. Letztere erhielt man durch Reduktion der -substituierten Emodine.

     

A general and efficient stereoselective synthesis of γ-azido-tetrahydrofuran carboxylic acids from glycals

An efficient, direct and general synthesis of enantiopure γ-azido-tetrahydrofuran carboxylic acid monomers (5-8) from commercially available glycals, suitable to design peptidomimetic oligomers with predisposed conformation, is described. The single crystal X-ray study of 8 showed that the compound crystallized in orthorhombic space group. The crystal-packing showed the presence of weak intermolecular C-H?O and aliphatic C-H?π interactions.     

Synthesis of aza-crown compounds by intramolecular cyclization of ω-amino acids

A method for the synthesis of aza-crown compounds by the intramolecular cyclization of -amino acids with subsequent reduction of the lactam to a macrocyclic amine was developed. 1,8-Diazacyclotetradecane and 1,8-dioxa-4,11-diazacyclotetradecane were synthesized in preparative yields. The structural assignments were made using the IR, ¹H and ¹³C NMR, and mass spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 247–255, February, 1992.     

The hydroalumination of ω-terbutoxy alkynes an easy access to ω-hydroxy alkenyl iodides application to the synthesis of dienic insect pheromones

In contrast to classically protected ω-hydroxy alkynes, ω-terbutoxy alkynes undergo smooth hydroalumination with DIBAL-H. The obtained E or Z alkenyl alanes are iodinated leading to E or Z alkenyl iodides. The ω-terbutoxy group is easily converted into an acetate. The latter compounds are useful synthons for the synthesis of insect pheromones as examplified with two cases.     

Production of ω-3 polyunsaturated fatty acids from cull potato using an algae culture process

Algal cultivation for converting cull potato to docosahexaenoic acid (DHA) was studied. Schizochytrium limacinum SR21 was selected as the better producing strain, compared with Thraustochytrium aureum because of higher cell density and DHA content. Used as both carbon and nitrogen source, an optimal ratio of hydrolyzed potato broth in the culture medium was determined as 50%, with which the highest production of 21.7 g/L dry algae biomass and 5.35 g/L DHA was obtained, with extra glucose supplemented. Repeat culture further improved the cell density but not fed batch culture, suggesting limited growth was most likely caused by metabolites inhibition.