Furan derivatives. Part 8 On substituent effects in the synthesis of 4,5-dihydro-3H-naphtho[1,8-bc]furans

4,5-Dihydro-3H-naphtho[1,8-bc]furans 4 and 6 which have various substituents (R¹ and R²) have been synthesized from 8-oxo-5,6,7,8-tetrahydro-1-naphthyloxyacetic acids 1 and 3 or their ethyl esters 2 . The reaction of acids 1 and 3 with sodium acetate in acetic anhydride gave a mixture of furans 4 and 6 and lactones 5 and 7 . The ratios of the products were varied according to the types of substituents (R¹ and R²) in acids 1 and 3 . As the substituent R¹ (R² = hydrogen) in acids 1 was changed from hydrogen to a methyl, ethyl or isopropyl group, production of furans 4 became more difficult. However, when a phenyl group was used as the substituent, furan 4 was obtained in good yield. Similarly, as the substituent R² (R¹ = hydrogen) in acids 1 was changed from hydrogen to a methyl, ethyl or isopropyl group, furan formation was more difficult. In contrast, acids 3 which had electron-withdrawing substituents such as chlorine, bromine or a nitro group at the 4-position afforded furans 6 in good yield. 4,5-Dihydro-3H-naphtho[1,8-bc]furans 4 and 4,5-dihydro-3H-naphtho[1,8-bc]furan-2-carbocylic acids 8 were synthesized from the reaction of esters 2 and potassium hydroxide in dioxane. When the substituents R¹ or R² in esters 2 were varied from hydrogen to a methyl, ethyl or isopropyl group the total yields of furans 4 and furancarboxylic acids 8 were reduced.     

Pyrolysis of Amino Acid Derived Stabilised Ylides as a Route to Chiral Acetylenic Amines and Amino Acids and Gaba Analogues

Abstract

We recently reported the pyrolysis of stabilised ylides as a method for overall conversion of carboxylic acids to homologous acetylenic esters and terminal alkynes.^1,2 This has now been applied successfully to amino acids. A wide range of alkoxycarbonyl protected amino acids have been converted to the stable crystalline ylides 1. These have been fully characterised, and upon FVP, eliminate Ph₃PO to afford the protected acetylenic amino acids 2 in good yield and without significant racemisation. Subsequent reactions of these extremely versatile intermediates have been used to gain access to a wide variety of chiral amine and amino acids of great interest as potential selective enzyme inhibitors and components for modified peptide structures.     

Effects of ring substituents on enantioselective recognition of amino alcohols and acids in uryl-based binol receptors

The uryl-based binol aldehyde, (S)-2-hydroxy-2′-(3-phenyluryl-benzyl)-1,1′-binaphthyl-3-carboxaldehyde (1), binds 1,2-amino alcohols and amino acids stereoselectively by reversible formation of imine bond. Hydrogen bond (between uryl group and alcohol -OH moiety) plays an important role in the stereoselectivity of amino alcohols. Hence, any substituents on phenyl group in 1 are expected to affect H-bond ability of uryl group. To study the effects of ring substituents on the stereoselective recognition of amino alcohols, (substituted phenyl)uryl-based chiral binol receptors have been prepared. The receptors with electron-donating X substituents have been synthesized from (S)-2-methoxymethoxy-2′-hydroxy-1,1′-binaphthyl-3-carboxaldehyde and X-phenyluryl-benzyl bromide. The receptors with electron-withdrawing Y substituents, however, required a different synthetic strategy including transformation of an aldehyde to alcohol. The incorporation of the electron withdrawing groups slightly accelerated the stereoselective recognition property of the receptor. Though the acceleration is not so remarkable, this work demonstrates the versatile derivatization of 1 in achieving higher stereoselective recognition of 1,2-amino alcohols and stereoconversion of l-amino acids to d-amino acids.     

Determination of the Stability Constants of Inclusion Complexes of p-H-37-(2-carboxy-methyloxy)-calix-[6]-arene and p-sulphonato-37-(2-carboxy-methyloxy)-calix-[6]-arene with 15 Amino acids by RP-HPLC

Reversed-phase high performance liquid chromatography (Separon SGX CN, UV detection at 254~nm and water as mobile phase) was applied to thestudy of the host–guest complexation ofp-H-37-(2-carboxy-methyloxy)-calix-[6]-arene (1) and p-sulphonato-37-(2-carboxy-methyloxy)-calix-[6]-arene (2)with 15 amino acids in the mobile phase. It was established that the formation ofthe inclusion complexes results in changes in the retention times and capacity factorsof amino acids. Stability constants of the complexes were determined. The variations instability constant values may be explained in terms of the different interactions, whichmay occur between amino acids and 1 and 2.     

Complexation of amino acids derivatives in water by calix[4]arene phosphonic acids

Series of the calix[4]arene phosphonic acids with various substituents at the lower rim was synthesized. Complexing properties of these receptors towards methyl esters of six amino acids strongly depended on the calix[4]arene conformation flexibility. The complex formation processes were monitored using ¹H NMR spectroscopy (deuterated phosphate buffer at pD 7.3, 22 °C) and association constant values were evaluated. Inherently mobile calix[4]arene molecule 3 occurred in cone conformation in aqueous solution turned out to be more effective in complexation of the basic amino acids methyl esters compared to the rigid 2 and flexible 4. Mixed 1:2 and 2:1 (host–guest) complexes were observed for compound 1 with all amino acids methyl esters.     

Potentiometric and NMR Study of Aminoalkylphosphinic Acids ZWD their Complexing Properties

Abstract

Ethylenediamine-tetrakis- [methylene(phenylphosphinic)] acid, piperidine [methylenephosphinio] acid and piperasine-bis- thylenephoaphinic] acid have been prepared by the method of Plaza and Grim¹ and Meier². Their dissociation constants and stability constants with Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Mn²⁺, Fe²⁺, Co²⁺ and Ni²⁺ have been determined. Study of the dependence of the ¹H, ³¹P and ¹³C NMR spectra of solutions of the acids mentioned above on the pH indicates similarity to amino acids than to analogous phosphonic acids.     

Monolayers of Chiral Calix[4]Resorcinarenes: Surface Pressure and Surface Potential Studies

Abstract

Chiral amphiphilic C-undecylcalix[4]resorcinarenes substituted with phenylethyl group or L(-)nore-phedrine were found to form well-organized mono-layers at the aqueous solution-air interface. The substituents, L(-)norephedrine and phenylethyl group, determined the area occupied by the molecule on the water subphase. Introduction of these substituents lead also to perpendicular dipole moments of the molecules in the monolayers ca. 6 times larger than those of the parent amphiphilic calixresorcinarene, CAL11. Interactions of the compounds with K⁺ were detected by the increase of the surface potential values measured at maximum packing of the monolayer. Addition of amino acids to the subphase lead to conformational changes in the monolayers evidenced by increased surface mean molecular area of the unmodified C-undecyl-calix[4]resorcinarene. These changes were explained by the formation of hydrogen bonds with the amino acids at the expense of hydrogen bonding between the calixarene molecules in the monolayer. In contrast to unsubstituted calixresorcinarenes, interactions of the L(-)norephedrine-and phenylethyl-substituted molecules with amino acids could be easily recognized by the decrease of surface potential and dipole moment in monolayers formed by these calixarenes on subphases containing amino acids. A significant drop in the surface potential and an increased area per molecule demonstrated more specific interactions with selected amino acids: L(-)norephedrine-substituted calixarene interacted with D-valine and the phenylethyl-substituted, with D-tryptophan.     

Thia- and Sulfonyl-Calix[4]Arene Methylphosphonous Acids: Synthesis,Structure, and Amino Acids Binding

Abstract

Thia- and sulfonyl-calix[4]arene methylphosphonous acids have been synthesized by hydrolysis of corresponding alkyl esters. Host-Guest complexation of the thiacalix[4]arene tetrakis-methylphosphonous acid with a series of 12 amino acids has been investigated by HPLC and molecular modeling methods. Stability constants of the complexes are within 530—10,140 M^?1 in water contained solution.     

Novel Synthesis of 2-(2-(3-Hydroxy-5-oxo-4-phenylthiophen-2(5H)-ylidene)-2-phenylacetamido)propanoic Acid Analogues and Their Anti-Inflammatory Properties

This article describes the reaction of 3,6-diphenyl-thieno[3,2-b]furan-2,5-dione 1 with different amino acids 2a–j in glacial acetic acid which afforded the 2-(2-(3-hydroxy-5-oxo-4-phenylthiophen-2(5H)-ylidene)-2-phenylacetamido)propanoic acid analogues 3a–j and also describes the reaction of 3,6-diphenyl-thieno[3,2-b]thiophene-2,5-dione 4 with different amino acids 5a–e in acidic medium to give 2-(2-(3-mercapto-5-oxo-4-phenylthiophen-2(5H)-ylidene)-2-phenylacetamido)propanoic acid analogues 6a–e. All the compounds have been screened for their anti-inflammatory activity against the carrageenan induced rat paw edema in albino rats. In the primary screening, some of the compounds exhibited appreciable activity.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Synthesis and Electrochemical Reduction of Nitro-Alkanephosphonates

Abstract

As a continuation of our research program [l, 2], directed to the synthesis of aminoalkanephosphonates, we present here the synthesis of 1-amino-nitroalkanephosphonid acids 5, prepared according to eq. 1. The electrochemical reduction of amino acids 5 to the derivatives 6 and 7 (eq. 2) have been investigated.     

Homocoupling of arylboronic acids catalyzed by dinuclear copper(I) complexes under mild conditions

An efficient protocol for C–C coupling has been developed using three iodo-bridged copper(I) complexes as catalysts. Complexes [CuI(bpy)]₂ (1), [CuI(phen)]₂·DMF (2), and [CuI(Mephen)]₂ (3) were successfully synthesized via solvothermal method (bpy = 2,2′-dipyridyl, phen = 1,10-phenanthroline, and Mephen = 2,9-dimethylphenanthroline). The self-coupling reaction of phenylboronic acid was selected as a model reaction to evaluate the catalytic property of the complexes. Moreover, this method tolerates various substituents on the arylboronic acids such as halogens, carbonyls, and nitro groups. It shows that the iodo-bridged Cu(I) center serves as the active site to activate molecular oxygen during the catalytic process. The result illustrates that these complexes were found to be excellent catalysts for self-coupling of arylboronic acids under mild conditions.

     

Synthesis of Monocyclic β‐Lactams via Cyclodehydration of β‐Amino Acids Using POCl3

Abstract

β‐Lactams 2 have been synthesized through a convenient use of POCl₃ via cyclodehydration of β‐amino acids 1.     

Rapid and Efficient Microwave‐Assisted Synthesis of N‐Carbamoyl‐L‐amino Acids

A rapid and efficient method for the synthesis of N‐carbamoyl‐L‐amino acids is reported. The procedure, involving the reaction between urea and α‐amino acids sodium salts, was performed under microwave conditions using an unmodified domestic microwave oven. A careful study of the operative conditions indicated proline (1d) as the less reactive substrate and phenylglycine (1e) as the more reactive one among all the α‐amino acids tested. Substitution of urea with potassium cyanate produced a low conversion into the corresponding N‐carbamoyl derivative, and a possible explanation of this result is reported.     

CYCLIC ORGANOPHOSPHORUS COMPOUNDS. PART XVI1. MASS SPECTROMETRIC FRAGMENTATION OF SOME 5,5-DIMETHYL-1,3,2-DIOXAPHOSPHORINAN 2-OXIDES AND 2-SULPHIDES

Abstract

The mass spectra of seventeen 5,5-dimethyl-1,3,2-dioxaphosphorinan 2-oxides and nineteen 5,5-dimethyl-1,3,2-dioxa-phosphorinan 2-sulphides, mostly with amino substituents on phosphorus, have been determined. In some cases, interpretation of the spectra was aided by accurate mass measurements and by the examination of deuterated compounds. For the 2-sulphides, sulphur is lost either as such or as the thiol radical, both processes often being of weak intensity, and the thiol hydrogen appears to be derivable from either a ring methylene group or a C-5 methyl group. Loss of S or HS occurs more strongly for the phosphoramidothionates which, together with the phosphoramidates, also fragment to an important extent in the amido substituent with retention of the dioxaphosphorinan ring; P[sbnd]N bond cleavage is also observed. For the 2-thiones, the ions at m/e 165 (14; R[dbnd]H) and 133 (15; R[dbnd]H) are characteristic.     

Direct Formation of Cycloadducts Between Fullerenes and Amino Acids Through Electron-Transfer Processes

Abstract

The reactions of [60]fullerene and amino acids in the absence of aldehyde in o-dichlorobenzene (ODCB) at 150 °C have been investigated. Fulleropyrrolidines 1 [C₆₀(CH₂N(CH₃)CHC₆H₂(NO₂)₃)], 2 [C₆₀(CH₂N(CH₃)CH₂)], 3 [C₆₀(CH₂NHCH₂)], and 5a–b [C₆₀(RCHNHCHR), R?CH₃ (5a), R?CH₂Ph (5b)] were obtained in moderate yields from the reactions of C₆₀ and corresponding amino acids. The reaction of C₇₀ and N-methylglycine in the absence of aldehyde was also studied and was found to give the positional isomers of N-methyl[70]fulleropyrrolidines 6 (1,9-isomer) and 7(7,8-isomer). All products were fully characterized by ultraviolet–visible, Fourier transform–infrared (FT-IR), NMR, and mass spectrometry. The reactions were also carried out in the dark to exclude the possible interference of the photoinduced reactions, and almost the same yields of products were obtained.     

Complexation of thiacalix[4]arene methylphosphonic and sulphonic acids with amino acids

In this paper, host–guest complexation process of thiacalix[4]arene tetrakis–methylphosphonic and tetrakis–sulphonic acids with amino acids by HPLC and molecular modelling methods has been studied. It was shown that thiacalix[4]arene tetrakis–methylphosphonic acid due to transformability of macrocyclic skeleton and flexibility of methylphosphonic substituents can adopt its conformation for strong multicentre binding of the amino acids with association constant values 530–10,140 M^? 1 in water.     

Multiwavelength Spectrophotometric Determination of Dissociation Constants of Mercaptopyrimidines

Abstract

The dissociation constants of some 2- and 6-mercaptopyrimidine derivatives with amino or hydroxy substituents are reported. The constants have been determined at 25° C in 0.1 M KCl aqueous solution. The multiwavelength spectrophotometric data obtained have been 3mlyzed by means of the SQUAD program (Stability Quotients from Absorbance Data).     

Synthesis and amino acid extraction abilities of chiral calix[4]arene triamides containing amino alcohol units

Herein the synthesis and extraction abilities of new d-/l-phenylalaninol substituted p-tert-butylcalix[4]arene triamide derivatives (3 and 4) towards amino acids are reported. These compounds (3 and 4) have been easily synthesized via aminolysis of p-tert-butylcalix[4]arene trimethylester (2) with d-/l-phenylalaninol in methanol-toluen solvent system at one step. The extraction properties of the prepared chiral calix[4]arene triamide derivatives (3 and 4) towards some selected amino acid methylesters are studied by liquid–liquid extraction. Results show that these chiral calix[4]arene triamide derivatives (3 and 4) exhibited a good affinity towards all amino acid species without any remarkably discrimination.     

Design and Syntheses of Novel Calix[4](aza)crowns: Neutral Receptors for α‐Amino Acids

A series of novel calix[4](aza)crowns 2a–2d containing acylhydrazone groups was designed and synthesized via 1+1 condensation of calix[4]‐1,3‐substituted benzaldehyde derivative 1 with bis‐hydrazides in 85–90% yields. They showed good complexation abilities toward α‐amino acids and exhibited complexation selectivity toward tryptophane.     

Densities of aqueous solutions containing model compounds of amino acids and ionic salts at T = 298.15 K

Densities of amino acids in aqueous and in aqueous electrolyte solutions have been measured by a high precision vibrating tube digital densitometer at T = 298.15 K under atmospheric pressure. The investigated systems contained amino acids of zwitterionic glycine peptides: glycine (Gly), diglycine (Gly₂), triglycine (Gly₃), and tetraglycine (Gly₄) and cyclic glycylglycine (c(GG)) with electrolytes of potassium chloride (KCl), potassium bromide (KBr) and potassium acetate (KAc). In this series of measurements, the aqueous samples were prepared with various concentrations of the amino acids, up to saturated conditions, and over salt concentrations from 1 to 4 M. The density increments resulting from the addition of the different model compounds of amino acids and the ionic salts were investigated, respectively. An empirical linear combination equation with an augmented term to account the interactions between amino acid and ionic salt was used to quantitatively correlate the experimental densities over the entire concentration ranges.