Synthesis of N-glycoconjugates of glycyrrhetic acid

New N-glycoconjugates that are analogs of glycyrrhizic acid were synthesized by condensation of α-L-rhamnopyranosylamine and β-D-lactosylamine with acid succinate and phthalate of glycyrrhetic acid methyl ester using N,N′-dicyclohexylcarbodiimide (DCC) or DCC-N-hydroxybenzotriazole. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 54–56, January–February, 2006.     

Ring‐opening metathesis polymerization of amino acid‐functionalized norbornene derivatives

Amino acid‐derived novel norbornene derivatives, N,N′‐(endo‐bicyclo[2.2.1] hept‐5‐en‐2,3‐diyldicarbonyl) bis‐L ‐alanine methyl ester (NBA), N,N′‐(endo‐bicyclo[2.2.1]hept‐5‐en‐2,3‐diyldicarbonyl) bis‐L ‐leucine methyl ester (NBL), N,N′‐(endo‐bicyclo[2.2.1]hept‐5‐en‐2,3‐diyldicarbonyl) bis‐L ‐phenylalanine methyl ester (NBF) were synthesized and polymerized using the Grubbs 2nd generation ruthenium (Ru) catalyst. Although NBA, NBL, and NBF did not undergo homopolymerization, they underwent copolymerization with norbornene (NB) to give the copolymers with M_n ranging from 5200 to 38,100. The maximum incorporation ratio of the amino acid‐based unit was 9%, and the cis contents of the main chain were 54–66%. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5337–5343, 2006     

2-Azabicyclo[2.2.1]heptane-3-carboxylic acid - A bicyclic proline

Diels-Alder reaction of cyclopentadiene and methyl N-carbobenzyloxy-2-iminoacetate generated in situ from methyl 2-chloro-N-carbobenzyloxyglycinate by triethylamine gave the N-carbobenzyloxy unsaturated bicyclic proline ester. This was converted in two steps to 2-azabicylo[2.2.1]heptane-3-carboxylic acid. In contrast to N-carbobenzyloxy-L-proline methyl ester, the corresponding bicyclic proline ester was resistant to hydrolysis catalyzed by carboxypeptidase Y.     

NMR spectroscopy in distinguishing between 3-piperidyl- and 2-pyrrolidylmethyl alcohols,amines, esters,and amides

Nmr analysis was found to be superior to an older ir technique for assigning structures in a study involving ring contraction-expansion of 3-hydroxypiperidine ? 2-hydroxymethylpyrrolidine systems and their ester derivatives. Nmr was not useful in studies of 3-aminopiperidines and 2-aminomethylpyrrolidines, but it could be applied to certain of their N-acyl derivatives. The nmr method was used to determine that esterification reactions of 1-methyl-3-(p-toluenesulfonyl)-piperidine and the sodium or potassium salts of some highly substituted carboxylic acids gave the ring-contracted pyrrolidine esters. In contrast, 1-methyl-3-aminopiperidine formed an amide with benzilic acid in which the piperidine ring remained unchanged. Aminolysis of methyl benzilate with 1-methyl-3-aminopiperidine resulted in a novel decarbonylation of the ester and isolation of benzophenone and l-methyl-3-formylamidopiperidine.     

The evidence for complex formation between N-acetyl-l-tyrosine methyl ester and N-acetylprocainamide hydrochloride using NMR spectroscopy

In order to reveal the possible mechanism of the recognition of antiarrhythmic agents class I and class III by the amino acid residues, which are responsible for drug binding to the selectivity filters either in the sodium or potassium ion channels, co-crystallizations of procainamide hydrochloride and N-acetylprocainamide hydrochloride with N-acetyl-l-tyrosine methyl ester and N-acetyl-l-phenylalanine methyl ester were performed using various conditions. Because the crystallization of the complexes failed, the intermolecular interactions between the components were evidenced using NMR spectroscopy. Exclusively, in the case of N-acetylprocainamide hydrochloride and N-acetyl-l-tyrosine methyl ester, two-dimensional NMR experiments and Job Plot analysis indicated the formation of the 1:1 complex in DMSO-d ₆  solution (with the association constant of 16 M⁻¹), whereas for the mixture of procainamide hydrochloride with N-acetyl-l-tyrosine methyl ester, the complex formation was not confirmed. The NMR results were discussed using crystal structure data obtained for N-acetylprocainamide hydrochloride, procainamide hydrochloride, as well as procainamide dihydrochloride, and were compared with the known pharmacological activity of the antiarrhythmic agents.     

A New Route of Synthesis of 5‐(N‐Phenethylamino)salicylic Acid Derivatives by Rapid and Selective Reduction of the Amide Group with NaBH4/Acetic Acid

A good yield of 5‐(N‐phenethylamino)salicylic acid derivatives was successfully obtained from the corresponding methyl 2‐acetoxy‐5‐(N‐phenethylamino)benzoate esters by rapid and selective reduction of the amide group in the acyl protected salicylic acid with NaBH₄/acetic acid in dioxane followed by hydrolysis of the ester group.     

Reactions of N"-acyl- and N"-tosyl-substituted hydrazides of 2-aminobenzoic acid with carbonyl compounds

The reactions of N"-acyl and N"-tosyl-substituted hydrazides of 2-aminobenzoic acid with aliphatic, aromatic, and heterocyclic aldehydes or aliphatic ketones afforded 3-acyl- and 3-tosylamido-1,2-dihydroquinazolin-4-one derivatives, respectively. The structures of the reaction products were established by NMR spectroscopy and X-ray diffraction analysis.     

Synthesis and reaction of β‐hydroxyaspartic acid‐based polymethacrylate

O‐Methacryloyl‐N‐(tert‐butoxycarbonyl)‐β‐hydroxyaspartic acid dimethyl ester was synthesized by methyl esterification of β‐hydroxyaspartic acid, followed by protection of the amino group with the tert‐butoxycarbonyl group and then the reaction of the hydroxyl group with methacryloyl chloride. The monomer efficiently underwent radical polymerization to afford the corresponding polymer with a number‐average molecular weight of 42,000 in good yields. The alkaline hydrolysis of the polymer occurred not only at the methyl ester but also at the ester moiety between the main and side chains of the polymer. The methyl ester‐free polymer gradually released β‐hydroxyaspartic acid moiety in a phosphate buffer solution with pH = 7.3 and 7.8. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2782–2788, 2002     

Krafft temperature and enthalpy of solution of<Emphasis Type="Italic"> N</Emphasis>-acyl amino acid surfactants and their racemic modifications: effect of the counter ion

The Krafft temperatures and enthalpies of solution of N-hexadecanoyl alaninate and valinate, and N-tetradecanoyl phenylalaninate were obtained from differential scanning calorimetry. The Krafft temperature of N-acyl amino acid surfactant increased with decreasing size of the counter ion, with some exceptions. The enthalpy of solution was endothermic and increased with decreasing size of the counter ion except for the cases of lithium salt. The results showed that the L-L interaction in the solid state of N-hexadecanoyl amino acid surfactant salt was superior to the D-L interaction for both the alanine and valine systems when the counter ion size increased. However, the D-L interaction was still advantageous for the phenylalanine system with Cs⁺ as a counter ion. Both Fourier transform infrared spectroscopy studies and theoretical calculations suggested that the difference in magnitudes of the interactions between peptide and counter ion was a dominant factor for the chiral effect.     

Reaction of anthranilic acid amides with cyclic anhydrides

Anthranilic acid amide reacts with cyclic anhydrides to give the corresponding N-acyl derivatives at the amino group, while analogous reactions of o-aminobenzohydroxamic acid lead lead to formation of 3-hydroxy-quinazolin-4-ones under mild conditions. N-Acyl derivatives of anthranilic acid amide undergo intramolecular cyclization to imides on microwave irradiation or on melting, and their treatment with acetic anhydride in the presence of sodium acetate on heating yields quinazolin-4-ones.     

Nitrogen photochemistry. Cocaine and its model compounds

The ultraviolet irradiation of the π → π* transition of cocaine, p-anisoyl-l-ecognine methyl ester, p-toluoyl-l-ecognine methyl ester benzoyl tropine and benzoylpseudotropine in methanol using a Corex filter produces the corresponding N-demethylated products. Formaldehyde is quantitatively produced. 1-Methyl-3-piperidyl benzoate and 1-methyl-4-piperidyl benzoate yield benzoic acid under the same conditions but no demethylated products. Phenylacetyl-l-ecognine methyl ester gives no demethylation during irradiaiton. The phosphorescence bands of cocaine and its model compound, methyl benzoate, have been shown to be strongly dependent upon solvent polarity suggesting charge transfer in the triplet state.     

Polymerization of 2,5‐diaminoterephthalic acid‐type monomers for the synthesis of polyamides containing ladder unit

To synthesize ladder‐type polyamides by construction of two amide bonds successively, 2,5‐diaminoterephthalic acid derivatives bearing anthranilic acid ester and isatoic anhydride moieties were synthesized and their polymerization was investigated. Polymerization of the methyl ester monomer proceeded in the presence of lithium hexamethyldisilazide (LiHMDS) as a base in tetrahydrofuran (THF). However, mass spectroscopic analysis of the product suggested that not only the bis(trimethylsilyl)amide anion of LiHMDS but also the methoxide anion eliminated at the second amide‐linkage formation reaction decomposed the isatoic anhydride unit of the growing oligomer by nucleophilic attack to disturb the polymerization. To reduce the nucleophilicity of the eliminated anion, methyl ester of the monomer was changed to phenyl ester and its polymerization was studied. The reaction conditions were optimized, and the best result was obtained when the polymerization was conducted in the presence of 1.0 equivalent of LiHMDS without additives in THF at 50 °C. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2365–2372     

Alkaloids of Siberia and Altai flora: XVIII. Alkyl 2-acetylamino-5-[2-(pyridin-3-yl)vinyl]benzoates in the synthesis of indolizines containing an anthranilic acid ester moiety

Methyl 2-acetylamino-5-[2-(6-methylpyridin-3-yl)vinyl]benzoate reacted with phenacyl bromide to produce quaternary 1-(2-aryl-2-oxoethyl)-2-methyl-5-(4-acetylamino-3-methoxycarbonyl)pyridinium bromides. 1,3-Dipolar cycloaddition of the latter to methyl propynoate and dimethyl but-2-ynedioate gave the corresponding indolizine derivatives containing an anthranilic acid ester moiety. Reactions of acetylenes with N-phenacylpyridinium salts obtained from a diterpene alkaloid derivative, 2-(pyridin-3-yl)vinyl-substituted lappaconitine afforded analogous compounds in which the indolizine fragment is conjugated to the aromatic ring of the alkaloid. 1,3-Dipolar cycloaddition of 1-(2-aryl-2-oxoethyl)-2-methyl-5-(4-acetylamino-3-methoxycarbonyl) pyridinium bromides with methyl propynoate was regioselective.     

Rapid Synthesis of N-Acyl Ureas from Their Thio Analogues Using Wet Silica-Supported Permanganate Under Solvent-Free Conditions

A rapid method to N-acyl ureas from corresponding N-acyl thioureas is described. N-coumaroyl-N′-arylthioureas, which are easily prepared by the reaction of coumarin-3-carboxylic acid chloride with potassium thiocyanate and arylamines, can be expeditiously transformed into corresponding N-acyl ureas via r.t. grinding with wet silica supported potassium permanganate under solvent-free conditions in an excellent yield.     

X-ray diffraction analysis and luminescence spectral study of crystal solvates of N-(N"-tosylanthranoyl)anthranilic acid with acetic acid and dimethylformamide

Two crystal modifications of N-(N"-tosylanthranoyl)anthranilic acid were studied by X-ray diffraction analysis and luminescence spectroscopy. One crystal modification is a crystal solvate with acetic acid and is characterized by green fluorescence. Another modification is a crystal solvate with DMF and exhibits blue fluorescence. The modifications differ in the melting point.     

Organic Base‐Catalyzed Stereoselective Isomerizations of 4‐Hydroxy‐4‐phenyl‐but‐2‐ynoic Acid Methyl Ester to (E)‐ and (Z)‐4‐Oxo‐4‐phenyl‐but‐2‐enoic Acid Methyl Esters

We have developed a 1,4‐diazabicyclo[2.2.2]octane (DABCO)‐catalyzed isomerization of 4‐hydroxy‐4‐phenyl‐but‐2‐ynoic acid methyl ester to (E)‐4‐oxo‐4‐phenyl‐but‐2‐enoic acid methyl ester and an N,N‐diisopropylethylamine‐catalyzed isomerization of the same substrate to (Z)‐4‐oxo‐4‐phenyl‐but‐2‐enoic acid methyl ester.     

Si-Containing Amides of Phosphoric Acid

Summary. The first representative of the N-silylmethylamides of phosphoric acid O=P[NMe(CH₂SiMe _n (OEt)_3-n ]₃ have been synthesized by interaction of MeNHCH₂SiMe _n (OEt)_3-n (n = 2, 3) with POCl₃. The interaction of the N,N′,N″-trimethyl-N,N′,N″-tris[(ethoxydimethyl- silyl)methyl]triamide phosphoric acid with BF₃·Et₂O or BCl₃ results in the formation of the N,N′,N″-trimethyl-N,N′,N″-tris[(fluorodimethyl-silyl)methyl]triamide phosphoric acid or N,N′,N″-trimethyl-N,N′,N″-tris[(chlorodimethylsilyl)methyl]triamide phosphoric acid. NMR data show on the tetracoordinate state of silicon in these products. Professor Vadim Aleksandrovich Pestunovich, our chief, teacher and friend died on July 4^th, 2004     

Xanthobilirubic acid and its amides. Synthesis,spectroscopy, and solution structures

Xanthobilirubic acid, 5-[1,5-didehydro-3-ethyl-4-methyl-5-oxo-2H-pyrrol-2-ylidene)methyl]-2,4-dimethyl-1H-pyrrol-3-propanoic acid, its methyl ester, amide, N-methylamide and dimethylamide, and kryptopyrromethenone have been synthesized and characterized spectroscopically. In d₆-DMSO solution all pyrromethenones were monomeric, with lactam and pyrrole N-Hs H-bonded to solvent. In deuteriochloroform, the pyrromethenones preferred a dimeric form, with intramolecular H-bonding between the lactam C = 0 of one unit and the lactam and pyrrole N-Hs of the second.     

Use of N‐methyliminodiacetic acid boronate esters in suzuki‐miyaura cross‐coupling polymerizations of triarylamine and fluorene monomers

Polytriarylamine copolymers can be prepared by Suzuki‐Miyaura cross‐coupling reactions of bis N‐methyliminodiacetic acid (MIDA) boronate ester substituted arylamines with dibromo arenes. The roles of solvent composition, temperature, reaction time, and co‐monomer structure were examined and (co)polymers prepared containing 9, 9‐dioctylfluorene (F8), 4‐sec‐butyl or 4‐octylphenyl diphenyl amine (TFB), and N, N′‐bis(4‐octylphenyl)‐N, N′‐diphenyl phenylenediamine (PTB) units, using a Pd(OAc)₂/2‐dicyclohexylphosphino‐2′,6′‐dimethoxybiphenyl (SPhos) catalyst system. The performance of a di‐functionalized MIDA boronate ester monomer was compared with that of an equivalent pinacol boronate ester. Higher molar mass polymers were produced from reactions starting with a difunctionalized pinacol boronate ester monomer than the equivalent difunctionalized MIDA boronate ester monomer in biphase solvent mixtures (toluene/dioxane/water). Matrix‐assisted laser desorption/ionization mass spectroscopic analysis revealed that polymeric structures rich in residues associated with the starting MIDA monomer were present, suggesting that homo‐coupling of the boronate ester must be occurring to the detriment of cross‐coupling in the step‐growth polymerization. However, when comparable reactions of the two boronate monomers with a dibromo fluorene monomer were completed in a single phase solvent mixture (dioxane + water), high molar mass polymers with relatively narrow distribution ranges were obtained after only 4 h of reaction. © 2017 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2798–2806     

1,6- and 1,7-naphthyridines. II. Synthesis from acyclic precursors

A number of 8-hydroxy-6-methyl-1,6-naphthyridin-5(6H)-one-7-carboxylic acid alkyl esters 3 and the isomeric 5-hydroxy-7-methyl-1,7-naphthyridin-8(7H)-one-6-carboxylic acid alkyl esters 4 were synthesized from acyclic precursors obtained starting from quinolinic anhydride 5. Thus, methanolysis of 5 afforded the hemiester 6 which treated with oxalyl chloride and sarcosine ethyl ester gave 3-(N-ethoxycarbonylmethyl-N-methylcarbamoyl)pyridine-2-carboxylic acid methyl ester 8. Compound 8 was cyclized to naphthyridines 3a-e with sodium alkoxides. The isomeric naphthyridines 4a-c were obtained by cyclization of the open intermediary 2-(N-ethoxycarbonylmethyl-N-methylcarbamoyl)pyridine-3-carboxylic acid methyl ester 9 obtained by a route that involves treatment of 5 with sarcosine ethyl ester and esterification with diazomethane. Spectroscopic properties (¹H nmr, uv, ir) of compounds 3 and 4 are discussed and confirmed the proposed structures.