Polyenolates of Unsaturated Carboxylic Acids in Synthesis. Synthesis of Unsaturated α-Amino Acids and β-Hydrazing Acids

Regioselective reaction of lithium diene-and triene-diolates 1 and 2 with O-diphenylphosphinyl hydroxylamine affords unsaturated α-amino acids 3 and 4. Addition to DEAD leads selectively to γ-hydrazino unsaturated acids 5 and 6.     

Boron-Catalyzed α-Functionalizations of Carboxylic Acids

Catalytic, chemoselective, and asymmetric α-functionalizations of carboxylic acids promise up-grading simple feedstock materials to value-added functional molecules, as well as late-stage structural diversifications of multifunctional molecules, such as drugs and their leads. In this personal account, we describe boron-catalyzed α-functionalizations of carboxylic acids developed in our group (five reaction types). The reversible boron carboxylate formation is key to the acidification of the α-protons and enolization using mild organic bases, allowing for chemoselective and asymmetric bond formations of carboxylic acids. The ligand effects on reactivity and stereoselectivity, substrate scopes, and mechanistic insights are summarized.     

Spectrometric Study of α-Phenylcinnamic Acids

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Reactivity of N-Arenesulfonyl-ε-aminocaproic Acids

N-Arenesulfonyl--aminocaproic acids behave in aqueous dioxane as weak dibasic acids; their ionization constants were determined. The correlation of pK _a with Hammett constants was revealed, and the reaction parameters were evaluated. The reaction centers (carboxy and amide groups) are weakly sensitive to the effect of substituents in the benzene rings. Formation of an intramolecular hydrogen bond in the molecules of these acids was proved.     

The Synthesis of Cyclic Amino Acids

Several cyclic amino acids (1-4) were synthesized from glycine. Isocyanate ester was prepared as the key intermediate and reacted with dibromoalkanes to afford the target compounds.     

Reaction of α-Pinene with Haloacetic Acids

The reactions of -pinene with chloro-, bromo-, and trichloroacetic acids, accompanied by isomerization of -pinene, were studied.     

Interactions of Night Blue with Nucleic Acids and Determination of Nucleic Acids Using Resonance Light Scattering Technique

The noncovalent interactions of night blue (NB) with several nucleic acids in buffer medium of Britton‐Robinson at pH 4.1 have been studied by spectroscopic methods. It is shown that the binding of NB with nucleic acids involves the J‐aggregation of NB molecules on the surface of nucleic acids. The aggregation was encouraged by polyanions nucleic acids, in which nucleic acids served for acting templates. In this connection, a new method of nucleic acids with sensitivity at nanogram level is proposed based on the measurement of enhanced resonance light scattering (RLS). The linear range of ctDNA, fsDNA and yRNA is 0.01—2.5, 0.03—2.5 and 0.04—1.0 μg/mL, respectively, and the corresponding detection limits (3s?) are 9.4, 7.3 and 5.7 ng/mL at 2.5 × 10–⁵mol/L of NB. Synthetic and real samples were analyzed with satisfactory results.     

A Method for Preparing Phosphinic Acids from Hypophosphites: III. Synthesis of α-Hydroxy Phosphinic Acids

A one-pot method is proposed for preparing unsymmetrical -hydroxy phosphinic acids from ammonium hypophosphite. Bis(trimethylsilyl) phosphonites formed in situ on addition of bis(trimethylsilyl) hypophosphite to activated unsaturated compounds are brought without isolation into the Abramov reaction with an aldehyde or ketone. A series of new -hydroxy phosphinic acids are obtained.     

Synthesis of Optical Active 2-Arylpropionic Acids

2-Arylpropionic acid and its derivatives are pharmaceutically and agriculturally useful products1,2, especially, the optical isomer possesses extra higher biological or pharmaceutical activity, for example the antiflammatory agent3 of S-2-(6(-methoxyl- (-naphthyl) propionic acid (Naproxen), the effect of (S)-isomer is 28 times as actives as its R isomer. For the preparation of optically active 2-arylalkanoic acids many different synthetic strategies have been reported, such as, the resolution…     

Interaction of Hydroxy Acids with β-Cyclodextrin

The solubility of -cyclodextrin (-CD) was studied in aqueous solutions of various organic acids. The hydroxy acids, especially citric and tartaric acid were found to increase the solubility of -CD, while some other carboxylic acids reduced it. From solubility data the apparent complex association constants were calculated.     

Effect of Temperature on The Solubility of α-Amino Acids and α,ω-Amino Acids in Water

The aqueous solubilities of glycine, dl-α-alanine (2-aminopropanoic acid), dl-α-aminobutyric acid (2-aminobutanoic acid), dl-α-norvaline (2-aminopentanoic acid), dl-α-norleucine (2-aminohexanoic acid), β-alanine (3-aminopropanoic acid), γ-aminobutyric acid (4-aminobutanoic acid), 5-aminovaleric acid (5-aminopentanoic acid), and 6-aminocaproic acid (6-aminohexanoic acid) were determined from 293.15 to 323.15 K at intervals of 5.00 K using the gravimetric method. The temperature dependence of the solubility of α-amino acids and α,ω-amino acids in water is well described by the van’t Hoff equation. Linear van’t Hoff plots were used to determine the differential enthalpy of solution. The results obtained are compared with reported values in literature and are discussed in terms of the position of the ionic groups in the hydrocarbon chain.     

Diastereoselective Synthesis of Enantiopure Cyclic α-Aminophosphonic Acids

A new and efficient route for the synthesis of cyclic aminophosphonic acids by the reaction of dialkylchlorophosphites with β-aldiminoalcohols has been described.     

Synthesis of α-N-Ethylamino Acids and their Derivatives

 A new synthesis of α-N-ethylamino acids starting from α-amino acids using hexafluoroacetone as protecting and activating agent is described. The hexafluoroacetone-protected N-ethylamino acid derivatives obtained are activated lactons. Therefore, they can be directly transformed without the need of an additional activation step with various nucleophiles into the corresponding carboxylic acid derivatives.     

Synthesis of γ-Polynitrocarboxylic Acids And Derivatives Thereof

A synthesis of new branched -nitrocarboxylic acids and their derivatives (nitriles, amides, trinitroethyl esters) was developed proceeding from the corresponding aldehydes obtained by nitroform or 1,1-dinitroethane addition to 2-(2,2-dinitropropyl)acrylic aldehyde according to Michael reaction.     

How Lewis Acids Catalyze Diels–Alder Reactions

The Lewis acid(LA)-catalyzed Diels–Alder reaction between isoprene and methyl acrylate was investigated quantum chemically using a combined density functional theory and coupled-cluster theory approach. Computed activation energies systematically decrease as the strength of the LA increases along the series I₂<SnCl₄<TiCl₄<ZnCl₂<BF₃<AlCl₃. Emerging from our activation strain and Kohn–Sham molecular orbital bonding analysis was an unprecedented finding, namely that the LAs accelerate the Diels–Alder reaction by a diminished Pauli repulsion between the π-electron systems of the diene and dienophile. Our results oppose the widely accepted view that LAs catalyze the Diels–Alder reaction by enhancing the donor–acceptor [HOMO_diene–LUMO_dienophile] interaction and constitute a novel physical mechanism for this indispensable textbook organic reaction.     

Catalytic Asymmetric Hydrogenation of α-Acetamido Cinnamic Acids

Abstract

The homogeneous catalytic asymmetric hydrogenations of substituted cinnamic acids by (l-Benzyl-3,4-(R,R)-bis(diphenyl-phosphino) pyrrolidine (COD) Rh)BF₄ 6, easily prepared from L-tartaric acid has been studied. Contrary to other catalysts, this Rhodium (I) complex affords very high chemical and optical yields of N-acetylated amino acids under mild conditions even when using substrate to catalyst ratio as high as 16000. The method has been successfully applied for the preparation of L-Phenylalanine and L-Dopa.     

A New Asymmetric Synthesis of β-Aminophosphonic Acids

Addition of α-phosphonate carbanions to (S)-sulfinimines 2 gives N-sulfinyl-β-aminophosphonates 3 with a high diastereoselectivity (up to 10:1). The major diastereomer of 3 (R=Ph) was converted into (+)-(R)-β-amino-β-phenylethanephosphonic acid 5.     

Diels–Alder Reactions of β-Acylacrylic Acids

The Diels–Alder reaction of β-acylacrylic acids with dienes gave good yields and good regio- or stereoselectivity of the corresponding cycloaddition products with the use of Lewis acids.