Determination of Poly(3‐Hydroxybutyrate) using a Combination of Enzymatic Spectrophotometry and Alkaline Hydrolysis

Abstract

A combination of enzyme‐based spectrophotometric analysis and alkaline hydrolysis was developed for the measurement of poly(3‐hydroxybutyrate) (PHB). The principle of the determination is as follows: alkaline hydrolysis decomposes PHB into its monomer product 3‐hydroxybutyrate, which is followed with enzymatic reaction catalyzed by 3‐hydroxybutyrate dehydrogenase in the presence of nicotinamide adenosine dinucleotide (NAD). The product, nicotinamide adenosine dinucleotide with hydrogen (NADH) results in a spectrophotometric signal at 340 nm. This method shows high performance characteristics with simple operations.     

General and Facial Synthesis of 2‐Amino‐5‐halogenpyrimidine‐4‐carboxylic Acids and Their Derivatives

A facile synthetic approach to 2‐amino‐5‐halogen‐pyrimidine‐4‐carboxylic acids from 5‐halogen‐2‐methylsulfonylpyrimidine‐4‐carboxylic acid by nucleophilic displacement of the methylsulfonyl group with primary and secondary aliphatic amines has been developed. The titled amino acids underwent decarboxylation, yielding 2‐amino‐5‐halogenpyrimidines. Starting from 2‐amino‐5‐chloropyrimidine‐4‐carboxylic acid chlorides, 2‐[5‐chloro‐2‐(amino)‐4‐pyrimidinyl]‐2‐oxo‐1‐(2‐pyridyl)‐ethyl cyanides were obtained in excellent yields.     

Cross‐metathesis of C‐Glycosides and Peptides

Peptides bearing an acryloyl residue at their N‐terminus were coupled with various C‐glycosides in an equimolar ratio via cross‐metathesis. The newly formed olefin was obtained with high E/Z selectivity in satisfying to high yields with low homodimerization of the starting materials. The posttranslational cross‐metathesis approach was shown to be suitable for the combinatorial synthesis of a small library of C‐glycopeptides.     

Mild and Efficient Synthesis of 1,8‐Naphthalide and 1,8‐Naphthalenedimethanol

Abstract

Mild and efficient procedures have been developed for synthesis of 1,8‐naphthalide and 1,8‐naphthalenedimethanol. In an ice‐water bath, 1,8‐naphthalide was prepared from 1,8‐naphthlic anhydride using LiAlH₄ as reducing agent. 1,8‐Naphthalenedimethanol was obtained with good yield from reduction of 1,8‐naphthalic anhydride by LiAlH₄ and Lewis acids at room temperature. The effects of various factors on the reduction of 1,8‐naphthalic anhydride with LiAlH₄ were investigated.     

Crystal and Molecular Structure of 2‐nitro‐1‐ureidoguanidine

An Xray structural investigation of 2nitro1ureidoguanidine has been carried out. The crystals are monoclinic: a = 4.4690(2), b = 15.566(1), c = 9.4131(7), = 94.896(5)°, V = 652.4(3)> ³, space group P2₁/n, Z = 4, _calc = 1.650 g/cm³. The molecule consists of two planar fragments: carbamide and nitroguanidine. The geometrical characteristics of the molecule are analyzed. The system of intra and intermolecular hydrogen bonds in the crystal is considered.     

Affinity Adsorption Solid Substrate‐Room Temperature Phosphorimetry for the Determination of Alkaline Phosphatase

Abstract

In the presence of Pb(Ac)₂, the silicon dioxide nanoparticle containing rhodamine 6G (R‐SiO₂) can emit strong and stable solid substrate‐room temperature phosphorescence (SS‐RTP) signal on the surface of acetyl cellulose membrane (ACM) at λ_ex/λ_em=482/649 nm. It was found in the research that specific affinity adsorption reaction between triticum vulgare lectin (WGA) (which was labeled with luminescent silicon dioxide nanoparticle) and alkaline phosphatase (AP) can be carried out on the surface of ACM. The product of the reaction can emit stronger SS‐RTP signal. A new method of SS‐RTP for the determination of AP was established, based on an affinity adsorption reaction between AP and WGA labeled with nanoparticles containing rhodanime 6G luminescent molecules. The linear range of this WGA‐AP‐WGA‐R‐SiO₂ method is 1.00–360.00 ag AP spot^?1 (sample volume: 0.40 µL spot^?1, corresponding concentration range: 2.50–900.00 fg mL^?1). The regression equation of working curve is ΔIp=16.24+0.8856 m_AP (ag spot^?1), r=0.9993. Detection limit of this method calculated by 3S_b/k is 0.14 ag spot^?1. After 11‐fold replicate measurements, RSD are 3.9% and 3.1% for the systems containing 1.00 and 360.00 ag AP spot^?1, respectively. Compared with R‐SiO₂‐WGA‐AP method (detection limit: 0.45 ag spot^?1, corresponding concentration range: 2.00–320.00 ag spot^?1), the sensitivity of WGA‐AP‐WGA‐R‐SiO₂ method was obviously improved and the linear range was wider. The sensitivity, accuracy, and precision of this method are high. It has been successfully applied to determine AP in human serum.     

Crystal Structures of β‐1‐N‐Chloroacetamido Derivatives of d‐Glucose and d‐Galactose

Crystal structures of 1‐N‐(β‐d‐glucopyranosyl)chloroacetamide (1), an inhibitor of glycogen phosphorylase, and the corresponding galactopyranosyl amide (2) have been determined. Both crystals belong to P2₁2₁2₁ space group with 1 having the unit cell dimensions of a = 7.939(3), b = 9.547(3) and c = 14.157(2) Å, while those of 2 are, a = 7.636(10), b = 9.004(8) and c = 14.807(5) Å. The sugar ring takes a ⁴ C ₁ conformation and the amide linkage exists in Z‐anti conformation in both crystals. The torsion angle O5–C1–N1–C1′ is ? 93.9(5) for 1 and ? 111.5(3)° for 2. The conformational preference of Cl and N1 in 1 and 2 is found to be between anti and gauche. The molecular assembly in both 1 and 2 is stabilized by a finite chain of hydrogen bonds starting from N1H and ending at O1′, whereas a ten membered hydrogen‐bonded ring involving O4H and O5 is observed in 1.     

Synthesis and Application of Chitosan‐g‐PLLA Copolymers

The purpose of this paper is to study the synthesis and application of a new type of chitosan‐g‐poly(L‐lactide) copolymer with different grafting percentage in the presence of triethylamine. FTIR and ¹H NMR results indicate that grafting percentage of graft copolymers increases with the molar feeding ratio of L‐lactide to chitosan. The measurement of XRD and TG shows that graft copolymer exhibits low crystallinity and thermal degradation temperature. Static water contact angle testing suggests that graft copolymer has superior hydrophilicity compared with PLLA, which can be very useful for biomedical applications. 5‐Fluorouracil loaded copolymer microspheres were prepared by phase separation method. The size and distribution of microspheres were measured by a Laser particle analyzer. The microspheres with LLA:CS feeding molar rotio (15∶1) have a mean diameter of 332 nm with a narrow unimodal distribution. The spherical microspheres were observed by transmission electron microscopy (TEM). The microspheres shows good releasing property from drug release in vitro, and the drug release rate decreases as the increase of microspheres size.     

Novel Copolymers of Alkyl and Alkoxy Ring‐Substituted Ethyl 2‐Cyano‐3‐phenyl‐2‐propenoates and Styrene

Abstract

Electrophilic trisubstituted ethylenes, ring‐substituted ethyl 2‐cyano‐3‐phenyl‐2‐propenoates, RC₆H₄CH?C(CN)CO₂C₂H₅ (where R is 2‐CH₃, 3‐CH₃, 4‐CH₃, 2‐OCH₃, 3‐OCH₃, and 4‐OCH₃) were prepared and copolymerized with styrene (ST). The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring‐substituted benzaldehydes and ethyl cyanoacetate, and characterized by CHN analysis, IR, ¹H and ¹³C NMR. All the ethylenes were copolymerized with ST (M₁) in solution with radical initiation (AIBN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, ¹H and ¹³C NMR. The order of relative reactivity (1/r ₁) for the monomers is 3‐OCH₃ (0.88)?>?4‐CH₃ (0.71)?>?2‐OCH₃ (0.68)?>?3‐CH₃ (0.55)?>?2‐CH₃ (0.47)?>?4‐OCH₃ (0.40). Higher T _g of the copolymers in comparison with that of polystyrene indicates a decrease in chain mobility of the copolymer due to the high dipolar character of the TSE structural unit. Gravimetric analysis indicated that the copolymers decompose in the 257–287°C range.     

Synthesis and Characterization of Alkyl and Aryl‐(4‐methyl‐6‐nitro‐quinolin‐2‐yl)amines: X‐Ray Structures of Ethyl and Cyclohexyl‐(4‐methyl‐6‐nitro‐quinolin‐2‐yl)amine

Abstract

We have synthesized and characterized a series of alkyl and aryl‐(4‐methyl‐6‐nitro‐quinolin‐2‐yl)amines through a high‐yield, three‐step procedure starting from 4‐methylquinolin‐2‐ol. Nitration using concentrated nitric/sulfuric acids, followed by chlorination in phosphorus oxychloride, yielded 2‐chloro‐4‐methyl‐6‐nitro‐quinoline. All of the intermediates and aminated products have been characterized by multinuclear (¹H and ¹³C) NMR spectroscopy, elemental analysis, and, in the case of the two title compounds (ethyl and cyclohexyl‐(4‐methyl‐6‐nitro‐quinolin‐2‐yl)amine), a single crystal X‐ray structure was obtained to verify the nature of the new materials.     

Synthesis of Anomerically Pure,Furanose‐Free α‐Benzyl‐2‐amino‐2‐deoxy‐d‐altro‐ and d‐manno‐pyranosides and Some of Their Derivatives

The anomerically pure benzyl α‐d‐glycoside of 2‐amino‐2‐deoxy‐mannopyranoside was synthesized from d‐glucopyranose via 2‐amino‐2‐deoxy‐d‐altrose intermediates. Unlike the direct synthesis from mannosamine in the literature, our method provides furanose‐free products. A new method for the preparation of cis‐2,3‐oxazolidinones of 2‐amino‐2‐deoxy‐sugars was developed. A selective removal of the glycosidic benzyl group in the presence of 4,6‐O‐benzylidene protection was developed, which may provide new routes for the synthesis of oligosaccharides. Furanose‐free derivatives of α‐benzyl‐2‐amino‐2‐deoxy‐mannopyranuronic acids synthesized here offered possibilities for direct comparisons to prior literature preparations.     

Synthesis of 4‐Substituted‐ and 1,4‐Disubstituted‐4‐Hydroxypyrrolidin‐2‐ones

This report describes the synthesis of 4‐substituted‐ and 1,4‐disubstituted‐4‐hydroxypyrrolidin‐2‐ones by cyclization of intermediate γ‐aminoesters prepared from alkylbenzylamines, α‐bromoketones, and lithio ethyl acetate.     

Novel Copolymers of Styrene and Alkyl and Alkoxy Ring‐Trisubstituted Methyl 2‐Cyano‐3‐phenyl‐2‐propenoates

Electrophilic trisubstituted ethylene monomers, akyl and alkoxy ring‐trisubstituted methyl 2‐cyano‐3‐phenyl‐2‐propenoates, RC₆H₂CH[dbnd]C(CN)CO₂CH_3, (where R is 2,3‐dimethyl‐4‐methoxy, 2,5‐dimethyl‐4‐methoxy‐, 2,3,4‐trimethoxy‐, 2,4,5‐trimethoxy, 2,4,6‐trimethoxy, and 2,4‐dimethoxy‐3‐methyl), were synthesized by the piperidine catalyzed Knoevenagel condensation of ring‐substituted benzaldehydes and methyl cyanoacetate, and characterized by CHN elemental analysis, IR, ¹H‐ and ¹³C‐NMR. Novel copolymers of the ethylenes and styrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator (AIBN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H and ¹³C NMR, GPC, DSC, and TGA. High T_g of the copolymers in comparison with that of polystyrene indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. The gravimetric analysis indicated that the copolymers decompose in the 283–306°C range.     

Simple and Efficient One‐Pot Synthesis of 2,4‐Diaryl‐1,2,3‐triazoles

A general and efficient method for the preparation of 2,4‐diaryl‐1,2,3‐triazoles from α‐hydroxyacetophenones and phenylhydrazines is reported. The essential characteristics of this method include mild reaction conditions, a straightforward workup procedure, and comparatively higher yields.     

Alkaline‐Earth Metal Doped K‐V Catalysts for Diesel Soot Combustion–Preparation,Characterization and Catalytic Properties

The K‐V‐alkaline‐earth metal catalysts supported on α‐alumina ceramic substrate have been prepared. The morphology of the soot particulates deposited on prepared catalysts supported on α‐alumina ceramic substrate was described by scanning electron microscopy (SEM). The XRD was used to characterize the catalysts and their catalytic activities were evaluated by soot oxidation reaction using the TPR system. The SEM photographs presented that soot particles have a particle size of about 100 nm in diameter forming a loose contact with catalyst, which is resemble to the real situation for the catalyst application. The XRD and TPR study showed that the catalytic activities of the catalysts were improved through the cooperation of KNO₃ and some alkaline earth metal compounds. The soot onset ignition temperature at 310°C is the lowest by the cooperation of the crystalline phases KNO₃, KCaVO₄, and Ca₃(VO₄)₂ for the K‐V‐Ca catalyst with a molar ratio of 6:1:1. In addition, the catalyst containing higher KNO₃ content has an adsorption for CO₂. The all prepared K‐V‐Ba catalysts can adsorb more CO₂ at room temperature.     

Synthesis and NMR Characterization of Multi‐hydroxyl End‐groups PEG and PLGA‐PEG Barbell‐like Copolymers

Multi‐hydroxyl end‐groups poly(ethylene glycol) (PEG) was prepared from PEG and epichlorohydrin. Then, PEG‐supported poly(lactic‐ran‐glycolic acid) (PLGA)_n‐PEG‐(PLGA)_n (n=1, 2, 4) linear‐dendritic barbell‐like copolymers were synthesized through direct polycondensation under bulk condition from the multi‐hydroxyl end‐groups PEG, lactic acid and glycolic acid. Arm numbers were varied, with 2, 4 and 8, by using bis‐, tetra‐, and octa‐hydroxyl end‐groups PEG, respectively. The chemical structures, absolute number‐average molecular weight, the monomer units per single arm and the molar ratio of hydroxyl acid monomer units of the (PLGA)_n‐PEG‐(PLGA)_n barbell‐like copolymers were analyzed by NMR spectroscopy. The result indicated that the structures of the multi‐hydroxyl end‐groups PEG and (PLGA)_n‐PEG‐(PLGA)_n barbell‐like copolymers were consistent with design. Compared with the theoretical values, molecular weights determined by ¹H‐NMR end‐group analysis gave reasonably consistent values, but the values determined by gel permeation chromatography (GPC) were considerably less than theoretical values. The results indicated that (PLGA)_n‐PEG‐(PLGA)_n copolymers have linear‐dendritic structures.     

A Convenient and Efficient Preparation of 2‐Acetyl‐4,5‐difluorothiophene

A convenient, five‐step preparation of 2‐acetyl‐4,5‐difluorothiophene from 2,3‐dibromothiophene is described.     

Synthesis and Crystallographic Study of1,6‐bis‐(N‐phenothiazinyl)‐2,4‐hexadiyne

1,6‐bis‐(N‐phenothiazinyl)‐2,4‐hexadiyne (I) was synthesized in high yield by oxidative coupling of N‐propargyl phenothiazine. Grown from methylene chloride‐hexane solution, I is a monoclinic crystal, space group C2/c a=14.9500(18) Å; b=13.5512(15) Å; c=12.0116(10) Å; β=102.628(9)° Å; V=2374.6(4) ų. The intermolecular distances and arrangement of I in the unit cell preclude the usual diacetylene reactivity. Nevertheless, heating of I at 145°C results in decomposition of I to phenothiazine and a dark brown solid. In addition, cation‐radicals of I were prepared by oxidation with nitrosonium tetrafluoroborate and iodine to give stable ion‐radical salts.     

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.     

Novel Copolymers of Styrene and Alkoxy Ring‐Substituted 2‐Phenyl‐1,1‐dicyanoethylenes

Electrophilic trisubstituted ethylene monomers, ring‐substituted 2‐phenyl‐1,1‐dicyanoethylenes, RC₆H₄CH?C(CN)₂ (where R is 2‐methoxy, 3‐methoxy, 4‐methoxy, 4‐ethoxy, 4‐propoxy, and 4‐butoxy), were synthesized by piperidine catalyzed Knoevenagel condensation of ring‐substituted benzaldehydes and malononitrile, and characterized by CHN elemental analysis, IR, ¹H‐ and ¹³C‐NMR. Novel copolymers of the ethylenes and styrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator (AIBN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H and ¹³C NMR, GPC, DSC, and TGA. High T _g of the copolymers in comparison with that of polystyrene indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. The gravimetric analysis indicated that the copolymers decompose in the 290–450°C range.