Studies Towards the Synthesis of the β‐D‐Xyl‐(1 → 3)‐L‐ara Disaccharide Moiety of OSW‐1 from Ornithogalum saundersiae

Abstract

The OSW‐1 disaccharide having 2‐O‐p‐methoxybenzoyl‐β‐D‐xylopyranosyl‐(1 → 3)‐L‐arabinopyranoside structure was obtained as the benzylated 4‐O‐acetyl derivative 19. Also, the 4,2′‐di‐O‐acetate 18 was synthesized by a short synthetic approach. The arabinose acceptor 15 was obtained in a three step‐one pot sequence from easily available benzyl β‐L‐arabinopyranoside.     

Synthesis,Characterization and Photocrosslinking Properties of Poly(1‐(4‐Methacrylamidophenyl)‐1‐(4‐nitrophenyl)prop‐1‐en‐3‐one)

The phenylmethacrylamide monomer, 1‐(4‐methacrylamidophenyl)‐1‐(4‐nitrophenyl)prop‐1‐en‐3‐one (MPNP) containing a photosensitive group was synthesized by reacting 4‐nitrocinnamoylaniline with methacryloyl chloride in the presence of triethylamine at 0–5°C. The functional monomer, MPNP was polymerized in ethyl methyl ketone (EMK) under nitrogen atmosphere at 70°C using benzoyl peroxide (BPO) as the initiator. The synthesized polymer was characterized by UV, IR, ¹H‐NMR and ¹³C‐NMR spectroscopy. The molecular weight data of the polymer as obtained from gel permeation chromatography suggests a higher tendency for chain termination by radical recombination than disproportionation. The thermal studies of the polymer were obtained from thermogravimetric analysis. The glass transition temperature of the polymer was determined by differential scanning calorimetry. The solubility of the polymer was tested in various organic solvents at room temperature. The photosensitivity of the polymer was investigated in various solvents in the presence and absence of triplet photosensitizers. The effect of the different solvents nature and concentration on the rate of photocrosslinking of the polymer were also examined for using the polymer as negative photoresist materials.     

Sucrosyl‐(1 → 2)‐β‐Isomaltulose: Enzymatic Synthesis and Structure Determination

Abstract

By enzymatic reaction of sucrose (1) and isomelezitose (2) with the enzyme inulinase (NOVO, SP230) a novel tetrasaccharide (3) was synthesised,.the molecular weight of which was confirmed by electrospray‐ionisation mass spectrometry and gel permeation chromatography. Its structure was established by acid hydrolysis as well as ¹H and ¹³C NMR spectroscopy to be sucrosyl‐(1 → 2)‐β‐isomaltulose 3 (α‐D‐glucopyranosyl‐(1 → 2)‐β‐D‐fructofuranosyl‐(1 → 2)‐β‐D‐fructofuranosyl‐(6 → 1)‐α‐D‐glucopyranoside).     

Synthesis of the Branched Trisaccharide L‐Glycero‐α‐D‐manno‐heptopyranosyl‐(1 → 3)‐ [β‐D‐glucopyranosyl‐(1 → 4)]‐L‐glycero‐α‐D‐manno‐heptopyranose,Protected to Allow Flexible Access to Neisseria and Haemophilus LPS Inner Core Structures

Abstract

An efficient synthesis of the protected branched trisaccharide (2′S,3′S)‐(7‐O‐benzyl‐6‐O‐chloroacetyl‐3,4‐O‐(2′,3′‐dimethoxybutane‐2′,3′‐diyl)‐2‐O‐p‐methoxybenzyl‐L‐glycero‐α‐D‐manno‐heptopyranosyl)‐(1 → 3)‐[(2,3,4,6‐tetra‐O‐benzoyl‐β‐D‐glucopyranosyl)‐(1 → 4)]‐7‐O‐acetyl‐1,6‐anhydro‐2‐O‐benzyl‐L‐glycero‐β‐D‐manno‐heptopyranose, which is a key intermediate in the synthesis of inner core structures of Haemophilus and Neisseria LPSs, is described. The heptoses were formed by Grignard reactions using a benzyloxymethyl chloride or a commercial vinyl reagent. The anhydro bridge was formed by treatment of a 6‐OH methyl α‐heptoside precursor with FeCl₃. The protecting group pattern allows modifications at the 2‐, 3‐, 4‐, and 6‐positions of the second heptose moiety and also, after acetolysis of the anhydro bridge, elongation at the reducing end, all known alterations found in the bacterial LPSs.     

Synthesis of 4‐(Indol‐1‐yl)butanals via Rhodium‐Catalyzed Hydroformylation of 1‐Allylindoles

The rhodium‐catalyzed hydroformylation of new 1‐(β‐methallyl) indoles 1a–e carried out with Rh₄ (CO)₁₂ as the catalyst precursor, at 100 atm total pressure and 100°C, produces the 4-(indol‐1‐yl)‐3‐methylbutanals 2a–e as the sole products in high yields. The synthesized 4‐indolylbutanals are stable under the adopted conditions and are isolated and characterized here for the first time. The preparation of the starting 1‐allylindoles is described too.     

Asymmetric Synthesis of (2S)‐1‐(3,4‐Dihydroxyphenoxy)‐3‐(3,′4′‐Dimethoxyphenoxy) Ethylamino‐2‐propanol hydrochloride (RO363)

Enantiomerically pure (S)‐RO363 was synthesized by using (R,R) Salen Co(III) complex for the resolution of terminal epoxide. The hydrolytic kinetic resolution process was carried out at room temperature in excellent enantioselectivity. The method can be applied for large‐scale preparation of (S) RO363.     

Improved Synthesis of 1‐Hydroxy‐2,2,5,5‐tetramethyl‐3‐imidazoline 3‐Oxide (HTIO)

A simple, efficient, mild, and reproducible method for the synthesis of 1‐hydroxy‐2,2,5,5‐tetramethyl‐3‐imidazoline 3‐oxide is described. The method is based on the condensation of 2‐hydroxyamino‐2‐methylpropanal oxime with 2,2‐diethoxypropane in the presence of an equimolar quantity of acetic acid. Cost‐effectiveness of the condensation procedure could be also achieved by replacing 2,2‐diethoxypropane with less expensive 2,2‐dimethoxypropane.     

Efficient Synthesis of Trialkyl (E)‐3‐{3‐Oxo‐2‐3,4‐dihydro‐2‐(1H)‐quinoxalinylidene}‐prop‐1‐ene‐1,2,3‐tricarboxylates

The reaction of dialkyl acetylenedicarboxylates with alkyl 2‐[3‐oxo‐3,4‐dihydro‐2(1H)‐quinoxadinylidene]ethanoates in the presence of triphenylphosphine leads to trialkyl (E)‐3‐{3‐oxo‐2‐3,4‐dihydro‐2‐(1H)‐quinoxalinylidene}‐prop‐1‐ene‐1,2,3‐tricarboxylates in good yields.     

Effect of Triton‐X‐100 Solvent in the Micellar Catalysis of the Aquation of Tris(2‐nitroso‐1‐naphtholate) Ferrate (II)

The effect of triton‐X‐100 micelles on the aquation of Fe(C₁₀H₆N₂O)₃ ²⁺ has been investigated with triton‐X‐100 as solvent. In liquid triton‐X‐100, over a range of [H₂O] _T (0.0–3 M), significant rate enhancement factors of 50–150 are observe. Acid inhibits the rate of aquation at fixed [H₂O] _T . A mechanism based on effective solvent participation in a chemical environment similar to that in reversed micelles is proposed in liquid triton‐X‐100 with dispersed water pockets. This mechanism predicts direct H₂O substitution into the coordination sphere of Fe(C₁₀H₆N₂O)₃ ²⁺ in the highly polar water pockets or cavities where the Fe (II) complex molecules are solubilized. Changes in the tumbling rate, structure, and activity of water are suggested to account for the observed changes in the rate of aquation as a function OH [H₂O] _T . All k _ψ–[H₂O] _T profiles are structured and exhibit maxima with k _ψ(max) shifted to progressively higher [H₂O] _T as the fixed concentration [H⁺] _T is increased.     

Chiral (S)‐(+) 1‐Substituted Aryl‐4‐(1‐phenyl) Ethylformamido‐5‐amino‐1,2,3‐triazole: A New Class of Chiral Ligands for the Silver(I)‐Promoted Enantioselective Allylation of Aldehydes

Some novel chiral ligands, (S)‐(+) 1‐substituted aryl‐4‐(1‐phenyl) ethylformamido‐5‐amino‐1,2,3‐triazoles, were prepared starting from 1‐substituted aryl‐4‐ethoxycarbonyl‐5‐amino‐1,2,3‐triazoles and other reagents. They were used as catalytic chiral ligands in the silver (I)‐promoted enantioselective allylation reaction of aldehydes with allyltributyltin.     

Synthesis of (E)‐ and (Z)‐5‐(Bromomethylene)furan‐2(5H)‐one by Bromodecarboxylation of (E)‐2‐(5‐Oxofuran‐2(5H)‐ylidene)acetic Acid

(E)‐ and (Z)‐5‐(bromomethylene)furan‐2(5H)‐one have been prepared starting from the commercially available adduct between furan and maleic anhydride. A bromodecarboxylation reaction is a key step in the synthesis. The reaction gives the (E)‐ or (Z)‐5‐(bromomethylene)furan‐2(5H)‐one as the major product, dependent on the method used in the bromodecarboxylation.     

The Structure of N‐(1‐Deoxy‐β‐D‐fructopyranos‐1‐yl)‐L‐proline Monohydrate (“D‐Fructose‐L‐proline”) and N‐(1,6‐Dideoxy‐α‐L‐fructofuranos‐1‐yl)‐L‐proline (“L‐Rhamnulose‐L‐proline”)

Nano n-propylsulfonated γ-Fe₂O₃ was found to be a highly efficient, reusable heterogeneous catalyst for the conversion of a range of monosaccharides and some of their derivatives to the corresponding O-isopropylidene derivatives in good to excellent yields by refluxing the reaction mixture in dry acetone. The magnetic property of the catalyst enabled its separation from the reaction mixture by a simple process of filtration along with the aid of an external magnet. The efficiency of the catalyst was found to be largely unaffected for at least up to six cycles of reuse, thus proving the new methodology to be environmentally rewarding besides being simple and facile in operation.     

Synthesis of (±)‐ar‐Macrocarpene

An efficient first synthesis of the sesquiterpene ar‐macrocarpene, an irregular sesquiterpene isolated from Cupressus macrocarpa foliage, starting from 3‐methylcyclohexenone has been described, which confirmed the structures of macrocarpenes.     

Spectrophotometric Determination of Nitrite in Water Samples with 4‐(1‐Methyl‐1‐Mesitylcyclobutane‐3‐yl)‐2‐Aminothiazole

Abstract

A simple, sensitive, and specific spectrophotometric method for the measurement of nitrite in water has been developed and optimum reaction conditions along with other analytical parameters have been evaluated. The azo dye, 4‐(1‐methyl‐1‐mesitylcylobutane‐3‐yl)‐2‐(p‐N,N‐dimethylazobenzene)‐1,3‐thiazole was synthesized with the reaction of 4‐(1‐methyl‐1‐mesitylcylobutane‐3‐yl)‐2‐aminothiazole and N,N‐dimethyl aniline in acidic medium. Obtained azo dye has been characterized by infrared (IR), ¹H nuclear magnetic resonance (NMR), and microanalysis methods. The dye shows an absorption maximum at 482 nm. The method is optimized for acid concentration, pH, amount of reagents required, time, and interfering species. All the determinations were carried out at this wavelength throughout the work. At an analytical wavelength of 482 nm, Beer's law is obeyed over the concentration range 0.05 to 2.00 µg nitrite per mL analyte. The molar absorptivity, Sandell's sensitivity, and relative standard deviation are 2.03×10⁴ L mol^?1 cm^?1±251.3 (95%), 2.28×10^?3 µg cm^?2, and 2.74% (n=10), respectively. The detection limit of the method is 0.012 µg ml^?1 of nitrite ion. The method was succesfully applied to the determination of nitrite in tap water and lake water.     

Synthesis of Substituted 1‐\C\‐Phenyl‐D‐Tetritols and 1‐C‐(1H‐Pyrazol‐4‐yl)‐D‐tetritols by Ring Transformation of 2‐Formylglycals

Abstract

2‐Formylglycals 1a,b reacted with dialkyl 3‐oxoglutarates in the presence of base to furnish the 5‐[(1R,2R(S),3R)‐1,2,4‐tris(benzyloxy)‐3‐hydroxy‐butyl]‐2‐hydroxy‐isophthalic acid dialkyl esters 2a–d. Treatment of 1a,b with hydrazine derivatives afforded the substituted 1,2,4‐tri‐O‐benzyl‐1C‐(1H‐pyrazol‐4‐yl)‐D‐tetritols 5a–d. Deprotection of 5a,b was achieved with Pd/H₂ to yield the 1C‐(1‐methyl‐1H‐pyrazol‐4‐yl)‐D‐tetritols 6a,b.     

Electrochromic Properties of ‘Trimeric' Thiophene‐pyrrole‐thiophene Derivative Grown from Electrodeposited 6‐(2,5‐di(thiophen‐2‐yl)‐1H‐pyrrol‐1‐yl)hexan‐1‐amine and its Copolymer

A centrosymmetric polymer precursor, namely 6‐(2,5‐di(thiophen‐2‐yl)‐1H‐pyrrol‐1‐yl)hexan‐1‐amine (TPHA), was synthesized via a Knorr–Paal reaction using 1,4‐di(2‐thienyl)‐1,4‐butanedione and hexane‐1,6‐diamine. The resultant monomer was characterized by Nuclear Magnetic Resonance (¹H‐NMR). Electroactivity of TPHA was investigated via cyclic voltammetry. The electronic structure and the nature of electrochromism in P(TPHA) and its copolymer with EDOT, (P(TPHA‐co‐EDOT)), were examined via spectroelectrochemistry studies. P(TPHA) switches between claret red neutral state and blue oxidized state. Optical response times for coloring and bleaching processes of the P(TPHA) and P(TPHA‐co‐EDOT) were found as 2.1 s and 1.6 s, respectively.

The copolymer of TPHA was used to construct dual type polymer electrochromic devices (ECDs) against poly(3,4‐ethylenedioxythiophene) (PEDOT). Spectroelectrochemistry and electrochromic switching out of the devices were investigated.     

Microwave‐Assisted One‐Pot Synthesis of 2‐(Substituted phenyl)‐1H‐benzimidazole Derivatives

A series of 2‐(substituted phenyl)‐1H‐benzimidazole derivatives with various 5‐and 6‐position substituents (‐H, ‐CH₃, ‐CF₃) were synthesized via microwave irradiation using a short synthetic route and Na₂S₂O₅ as oxidant. This simple, fast, and efficient preparation of benzimidazole derivatives has been developed using readily available and inexpensive reagents (aldehydes and 1,2‐phenylenediamines) under solvent‐free conditions.     

Synthesis of the C‐Glycoside of Methyl α‐d‐Altropyranosyl‐(1→4)‐α‐d‐glucopyranoside

The C‐glycoside of methyl α‐d‐altropyranosyl‐(1→4)‐α‐d‐glucopyranoside 2 was prepared in a convergent fashion, from readily available precursors, 4‐O‐tert‐butyldiphenylsilyl‐1,2‐O‐isopropylidene‐d‐erythro‐S‐phenyl monothiohemiacetal 13 (five steps from D‐ribose) and the known acid, methyl 2,3,6‐tri‐O‐benzyl‐4‐C‐(carboxymethyl)‐4‐deoxy‐α‐d‐glucopyranoside 17 (seven steps from methyl α‐d‐glucopyranoside). The key reactions in the synthesis are the oxocarbenium ion cyclization of thioacetal‐enol ether 19 to a C1 substituted glycal 20, and the stereoselective hydroboration of 20 to the α‐C‐altroside 21.     

One‐Pot Synthesis of 2‐(1‐Alkyl/aralkyl‐1H‐benzimidazole‐2‐yl)‐quinoxaline Derivatives using Molecular Iodine

The title compound (5) has been prepared in one pot by refluxing 1‐(1‐alkyl/aralkyl‐1H‐benzimidazole‐2‐yl)‐ethanone (1) with substituted o‐phenylenediamine (2) in ethanol in the presence of iodine. Alternatively, 5 could also be prepared by treating 2‐bromo‐1‐(1‐ alkyl/aralkyl‐1H‐benzimidazole‐2‐yl)‐ethanone (3A) with 2 in refluxing ethanol. The formation of 5 from 1 and 2 probably occurs through the intermediacy of 3B (i.e., 3, X=I) and 4.