Microbial O‐demethylation of sinesetin and antimutagenic activity of the metabolite

Biotransformation of sinesetin by Aspergillus niger afforded 4′‐hydroxy‐5,6,7,3′‐tetramethoxyflavone on the basis of its spectroscopic data including IR, heteronuclear multiple quantum coherence (HMQC) and heteronuclear multiple bond connectivity (HMBC) analysis. Sinesetin and the metabolite showed antimutagenic activity against chemical mutagens 4‐dimethyl‐3H‐imidazo[4,5‐f]quinolin‐2‐amine (MeIQ) and 3‐amino‐14‐dimethyl‐5H‐pyrido[4,3‐b]indole (Trp‐P‐1) in the umu test using Salmonella typhimurium TA1535/pSK1002. Copyright © 2005 Society of Chemical Industry     

The antifungal activity and biotransformation of diisophorone by the fungus Aspergillus niger

The microbial transformation of racemic diisophorone was investigated using the plant pathogen Aspergillus niger as a biocatalyst. Incubation of diisophorone with Aspergillus niger gave 8α‐hydroxy‐diisophorone, 10‐hydroxydiisophorone and 17‐hydroxydiisophorone on the basis of their spectroscopic data including two‐dimensional NMR analysis, nOe and an X‐ray crystallographic study. The antifungal activity of diisophorone against Aspergillus niger was also examined. Copyright © 2004 Society of Chemical Industry     

Synthesis and fungicidal activities of polymeric biocides. I. TBZ-containing monomer and polymers

The fungicidal monomer, N-acryloyl-2-(4′-thiazolyl) benzimidazole (AcTBZ) was synthesized from 2-(4′-thiazolyl) benzimidazole (TBZ) and acryloyl chloride in the presence of triethylamine in dry benzene at 30°C. The synthesized AcTBZ was identified by IR and ¹H-NMR spectra. The homopolymers of AcTBZ were obtained using BPO as a thermal initiator in benzene under different experimental conditions such as various initiator concentrations or polymerization temperatures. The homopolymer of AcTBZ was also prepared using benzophenone as a photo initiator in DMF at 20°C. The average molecular weights (Mw ) of those poly(AcTBZ) s obtained were very low, being in the order of ca. 10³. Copolymer of AcTBZ and polymer of AcTBZ and acrylic acid (AA) was synthesized with thermal or photo initiators. Poly(AcTBZ) and poly(AcTBZ-co-AA) were identified by IR and ¹H-NMR spectra. The fungicidal activities of AcTBZ, poly(AcTBZ), and its polymers as well as TBZ against Aspergillus niger and Chaetomium globusum were very excellent compared to those of control polymers such as poly(AA) and poly(ethylene-co-vinyl acetate). The fungicidal activities were decreased in the order TBZ > AcTBZ > poly(AcTBZ) > poly(AcTBZ-co-AA) against both Aspergillus niger and Chaetomium globusum. The fungicidal activities of TBZ, and the synthesized AcTBZ and polymers containing AcTBZ were better against Chaetomium globusum than against Aspergillus niger. © 1994 John Wiley & Sons, Inc.     

Highly Regio‐ and Stereoselective Iodohydroxylation of Non‐ Heteroatom‐Substituted Allenes: An Efficient Synthesis of 4‐[3′‐Hydroxy‐2′‐iodoalk‐1′(Z)‐enyl]‐2(5H)‐furanone Derivatives

An efficient protocol for the highly regio‐ and stereoselective synthesis of 4‐(3′‐hydroxy‐2′‐iodoalk‐1′(Z)‐enyl)furan‐2(5H)‐one derivatives via selective iodohydroxylation of non‐heteroatom‐substituted allenes, i.e., 4‐allenyl‐2(5H)furanones, has been developed. The regio‐ and stereoselectivity of this reaction may be controlled by the electronic and steric effects of the furanone ring.     

Synthesis and characterization of novel polyphenol species derived from bis(4‐aminophenyl)ether: Substituent effects on thermal behavior,electrical conductivity,solubility, and optical band gap

In this study, four different Schiff bases namely 4,4′‐oxybis[N‐(2‐hydroxybenzilidene)aniline] (2‐HBA), 4,4′‐oxybis[N‐(4‐hydroxybenzilidene)aniline] (4‐HBA), 4,4′‐oxybis[N‐(3,4‐dihydroxybenzilidene)aniline] (3,4‐HBA), and 4,4′‐oxybis[N‐(4‐hydroxy‐3‐methoxybenzilidene)aniline] (HMBA) were synthesized. These Schiff bases were converted to their polymers that have generate names of poly‐4,4′‐oxybis[N‐(2‐hydroxybenzilidene)aniline] (P‐2‐HBA), poly‐4,4′‐oxybis[N‐(4‐hydroxybenzilidene)aniline] (P‐4‐HBA), poly‐4,4′‐oxybis[N‐(3,4‐dihydroxybenzilidene)aniline] (P‐3,4‐HBA), and poly‐4,4′‐oxybis[N‐(4‐hydroxy‐3‐methoxybenzilidene)aniline] (PHMBA) via oxidative polycondensation reaction by using NaOCl as the oxidant. Four different metal complexes were also synthesized from 2‐HBA and P‐2‐HBA. The structures of the compounds were confirmed by FTIR, UV‐vis, ¹H and ¹³C NMR analyses. According to ¹H NMR spectra, the polymerization of the 2‐HBA and 4‐HBA largely maintained with C? O? C coupling, whereas the polymerization of the 3,4‐HBA and HMBA largely maintained with C? C coupling. The characterization was made by TG‐DTA, size exclusion chromatography and solubility tests. Also, electrical conductivity of the polymers and the metal complex compounds were measured, showing that the synthesized polymers are semiconductors and their conductivities can be increased highly via doping with iodine ions (except PHMBA). According to UV–vis measurements, the optical band gaps (E_g) were found to be 3.15, 2.06, 3.23, 3.02, 2.61, 2.47, 2.64, 2.42, 2.83, 2.77, 2.78, and 2.78 for 2‐HBA, P‐2‐HBA, 4‐HBA, P‐4‐HBA, 3,4‐HBA, P‐3,4‐HBA, HMBA, PHMBA, 2‐HBA‐Cu, 2‐HBA‐Co, P‐2‐HBA‐Cu, and P‐2‐HBA‐Co, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Efficient Inhibition of Telomerase by Nickel–Salophen Complexes

Four nickel(II)–salophen complexes containing alkyl‐imidazolium chains connected at the ortho or meta positions were prepared: N,N′‐bis(2‐hydroxy‐4‐methyl‐3H‐imidazol‐1‐iumbenzylideneamino)phenylenediamine ( 1 ), N,N′‐bis(2‐hydroxy‐3‐methyl‐3H‐imidazol‐1‐iumbenzylideneamino)phenylenediamine ( 2 ), N,N′‐bis(2‐hydroxy‐3‐methyl‐3H‐imidazol‐1‐iumbenzylideneamino)methyl‐3H‐imidazol‐1‐iumphenylenediamine ( 3 ), and N,N′‐bis(2‐hydroxy‐4‐methyl‐3H‐imidazol‐1‐iumbenzylideneamino)methyl‐3H‐imidazol‐1‐iumphenylenediamine ( 4 ). They protect G‐quadruplex DNA (G₄‐DNA) against thermal denaturation and show K_A values in the range of 7.4×10⁵ to 4×10⁷ m ^?1 for G₄‐DNA models. Complex 4 exhibits an IC₅₀ value of 70 nm for telomerase inhibition.     

Biodegradable polymers: Photolysis and fungal degradation of poly(arylene keto esters)

Poly(keto esters) were prepared from 4,4′-bis(chloroacetyl) diphenyl ether, 4,4′-bis(bromoacetyl)diphenyl ether, and 4,4′-bis(2-bromopropionyl)-diphenyl ether and aliphatic diacids of 6, 8, 9, 10, and 12 carbon atoms. Low-molecular-weight polymers were found to support the growth of Aspergillus niger and Aspergillus flavus. Introduction of methyl group to the polymer chain decreased the susceptibility of the polymers to fungal attack. Although monomeric model compounds were found to undergo photodegradation the poly(keto esters) underwent mostly crosslinking when irradiated with UV light.     

Direct synthesis of poly(4′‐oxy‐4‐biphenylcarbonyl) and poly(2‐oxy‐6‐naphthoyl) under nonstoichiometric conditions

Direct synthesis of poly(4′‐oxy‐4‐biphenylcarbonyl) (POBP) and poly(2‐oxy‐6‐naphthoyl) (PON) was examined by polycondensation of 4′‐hydroxy‐4‐biphenylcarboxylic acid (HBPA) and 2‐hydroxy‐6‐naphthoic acid (HNA) in the presence of 4‐ethoxybenzoic anhydride or 2‐naphthoic anhydride as condensation reagents. Polymerizations were carried out at 320 °C in aromatic solvents and liquid paraffin. POBP, having a number‐average degree of polymerization (DPn) of 38, was obtained as plate‐like crystals at the molar ratio of HBPA and anhydride of 50 mol%. PON was also obtained as plate‐like crystals but the DPn was only 13. HBPA and HNA were first converted to reactive acyloxyaromatic acid intermediates. Then the DPn was increased by means of reaction‐induced crystallization of oligomers and subsequent solid‐state polymerization via an acid–ester exchange under nonstoichiometric conditions caused by the monocarboxylic acid by‐product. Even though the DPn of PON was not as high, direct polycondensation of HBPA and HNA proceeded successfully with aromatic anhydrides. Copyright © 2004 Society of Chemical Industry     

Effects of process parameters on heterologous protein production in Aspergillus niger fermentation

Filamentous fungi such as Aspergillus niger are attractive hosts for recombinant DNA technology because of their ability to secrete bioactive proteins with post‐translational processing such as glycosylation. Foreign genes can be incorporated into the chromosomes of the filamentous fungi, providing superior long‐term genetic stability. However, heterologous protein production is often severely hampered by fungal proteases. In this work, a recombinant Aspergillus niger strain AB4.1[pgpdAGLAGFP]#11 which carries a glucoamylase (GLA)‐green fluorescent protein (GFP) fusion gene was selected as a model system to study the effects of bioprocess parameters—agitation intensity, initial glucose concentration, initial yeast extract concentration, and dissolved oxygen tension (DO)—on extracellular protease inhibition and heterologous protein production. Based on previous experimental experience and results, a 2^4–1 fractional factorial design was applied to the experiments. Each parameter was tested at two levels. It was found that agitation affected the GFP production most significantly. Higher agitation rate resulted in higher GFP production. Protease activity was most influenced by initial glucose concentration and DO. Fungal morphology was also affected by these parameters. The effects of these parameters on pellet size and pellet porosity are discussed. Copyright © 2003 Society of Chemical Industry     

Reprogramming the Biosynthesis of Cyclodepsipeptide Synthetases to Obtain New Enniatins and Beauvericins

Non‐ribosomal peptide synthetases are complex multimodular biosynthetic machines that assemble various important and medically relevant peptide antibiotics. An interesting subgroup comprises the cyclodepsipeptide synthetases from fungi synthesizing cyclohexa‐ and cyclo‐octadepsipeptides with antibacterial, anthelmintic, insecticidal, and anticancer properties; some are marketed drugs. We exploit the modularity of these highly homologous synthetases by fusing the hydroxy‐acid‐activating module of PF1022 synthetase with the amino‐acid‐activating modules of enniatin and beauvericin synthetase, thus yielding novel hybrid synthetases. The artificial synthetases expressed in Escherichia coli and the fungus Aspergillus niger yielded new cyclodepsipeptides, thus paving the way for the exploration of these derivatives for their bioactivity.     

Enzymatic Synthesis of 1‐Alkyl‐2‐hydroxy‐sn‐glycero‐2,3‐cyclic‐phosphate Using a Novel Lysoplasmalogen‐Specific Phopholipase D

Many phospholipase Ds (PLDs) are known to catalyze transphosphatidylation as well as hydrolysis of phospholipids. Transphosphatidylation of lysoplasmalogen (LyPls)‐specific phospholipase D (LyPls‐PLD), which catalyzes hydrolysis of ether lysophospholipids such as LyPls and 1‐hexadecyl‐2‐hydroxy‐sn‐glycero‐3‐phosphocholine (Lyso‐PAF), still remains unclear. This study aims to reveal the transphosphatidylation activity of LyPls‐PLD, that is, the production of cyclic ether lysophospholipid. The enzymatic reaction is conducted in a buffer system, and the reaction products of a novel LyPls‐PLD from Thermocrispum sp. are investigated using mass spectrometry (MS). MS analyses demonstrate the reaction products to consist of 100% 1‐hexadecyl‐2‐hydroxy‐sn‐glycero‐2,3‐cyclic‐phosphate (cLyPA) and choline from Lyso‐PAF; however, 1‐alkenyl‐2‐hydroxy‐sn‐glycero‐2,3‐cyclic‐phosphate from 1‐O‐1′‐(Z)‐octadecenyl‐2‐hydroxy‐sn‐glycero‐3‐phosphocholine and 1‐O‐1′‐(Z)‐octadecenyl‐2‐hydroxy‐sn‐glycero‐3‐phosphoethanolamine is not produced. These results are expected to help in elucidating the catalytic mechanism of LyPls‐PLD, that is, the rate‐limiting step, and indicate LyPls‐PLD to be useful for the one‐pot synthesis of cLyPA. Practical Applications: A novel phospholipase D, LyPls‐PLD, can exclusively synthesize cLyPA from Lyso‐PAF using a one‐step enzymatic reaction without an organic solvent. cLyPA could be expected to show bioactivities similar to those of cyclic phosphatidic acid, which promotes normal cell differentiation, hyaluronic acid synthesis, antiproliferative activity in fibroblasts, and inhibitory activity toward cancer cell invasion and metastasis.     

Biocatalyzed Synthesis and Structural Characterization of Monoglucuronides of Hydroxytyrosol,Tyrosol, Homovanillic Alcohol,and 3‐(4′‐Hydroxyphenyl)propanol

The biocatalytic synthesis and purification of O‐β‐D ‐monoglucuronide conjugates of hydroxytyrosol, tyrosol, homovanillic alcohol, and 3‐(4′‐hydroxyphenyl)propanol, using porcine liver microsomes, are described here. The glucuronides were synthesized, analyzed and separated by HPLC‐UV, identified by HPLC‐MS, and their structures unequivocally established by NMR techniques. The outcome of the glucuronidation reaction depends on the structure of the phenolic compounds. Thus, the glucuronidation of hydroxytyrosol, biocatalyzed with porcine liver microsomes, proceeded exclusively on the phenolic hydroxy groups. The regioselectivity was similar to that observed for human and rat liver microsomes, the 4′‐hydroxy position being more favorable than the 3′‐hydroxy one. In the case of tyrosol, homovanillic alcohol, and hydroxyphenylpropanol, two products were formed during microsomal glucuronidation: a major one, the phenolic O‐β‐D ‐glucuronidated derivative and, a minor one, the O‐β‐D ‐glucuronidated aliphatic alcohol.     

Structure‐Based Design,Synthesis, and Evaluation of 2′‐(2‐Hydroxyethyl)‐2′‐deoxyadenosine and the 5′‐Diphosphate Derivative as Ribonucleotide Reductase Inhibitors

Analysis of the recently solved X‐ray crystal structures of Saccharomyces cerevisiae ribonucleotide reductase I (ScRnr1) in complex with effectors and substrates led to the discovery of a conserved water molecule located at the active site that interacted with the 2′‐hydroxy group of the nucleoside ribose. In this study 2′‐(2‐hydroxyethyl)‐2′‐deoxyadenosine 1 and the 5′‐diphosphate derivative 2 were designed and synthesized to see if the conserved water molecule could be displaced by a hydroxymethylene group, to generate novel RNR inhibitors as potential antitumor agents. Herein we report the synthesis of analogues 1 and 2 , and the co‐crystal structure of adenosine diphosphate analogue 2 bound to ScRnr1, which shows the conserved water molecule is displaced as hypothesized.     

Modulated gluconic acid production from immobilized cells of Aspergillus niger ORS‐4.410 utilizing grape must

BACKGROUND: Gluconic acid (GA) production by immobilized cells of mutant Aspergillus niger ORS‐4.410 on polyurethane sponge (PUS) and calcium‐alginate (Ca‐alginate) was evaluated in repeated batches of solid state surface fermentation (SSF) and submerged fermentation (SmF) conditions, respectively, utilizing rectified grape must as carbon source. RESULTS: The passive immobilization of cells in fermentation medium solid support of having 0.4 cm³ cube size, 4% spore suspension, 0.6 g inoculum of PUS immobilized cells at 32 °C and 2.0 L min^?1 resulted in the maximum GA production (88.16 g L^?1) with a 92.8% yield, while the Ca‐alginate matrix with a 0.5 cm diameter bead size, 2–3% spore suspension, 15 g inoculum at 34 °C and 150 rpm agitation speed revealed 67.19 g L^?1 GA with a 85.2% yield. Repeated use of PUS showed higher levels of GA (110.94 g L^?1) in the third–fourth fermentation cycles with 95–98% yield and 22.50 g L^?1 d^?1 productivity under SSF that was 2.5‐fold higher than the productivity obtained from a typical fermentation cycle, and 54% greater than the productivity obtained with repetitive use of Ca‐alginate immobilized cells of A. niger under SmF. CONCLUSION: Using immobilized cells of A. niger in PUS, the rectified form of grape must can be utilized for GA production as an alternative source of carbohydrate by replacing the conventional fermentation conditions. Copyright © 2008 Society of Chemical Industry     

Synthesis and photo‐ and biodegradabilities of poly[(hydroxybutyrate‐co‐hydroxyvalerate)‐ g‐phenyl vinyl ketone]

The graft copolymer, poly[(hydroxybutyrate‐co‐hydroxyvalerate)‐g‐phenyl vinyl ketone] [P(HBV‐g‐PVK)], was synthesized by graft polymerization of phenyl vinyl ketone (PVK) onto poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) under nitrogen atmosphere using benzoyl peroxide. The structure of P(HBV‐g‐PVK) was identified by Fourier transform IR and ¹H‐NMR spectra. The effects of weight ratio of PVK to PHBV in feed, initiator concentration, reaction time, and reaction temperature on the grafting ratio and grafting efficiency were investigated. The thermal decomposition temperature of P(HBV‐g‐PVK) was 272°C. The tensile strengths of P(HBV‐g‐PVK) after photo‐ or biodegradation were significantly decreased due to degradation by UV irradiation or Aspergillus niger. The value of color difference (ΔE) of P(HBV‐g‐PVK) was greater than that of PHBV. The film surfaces of P(HBV‐g‐PVK) treated with UV irradiation and Aspergillus niger showed many pits as compared with the untreated P(HBV‐g‐PVK). It has been found that the photo‐ and biodegradabilities of P(HBV‐g‐PVK) was excellent. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1432–1439, 1999     

A New Class of 3′‐Sulfonyl BINAPHOS Ligands: Modulation of Activity and Selectivity in Asymmetric Palladium‐Catalysed Hydrophosphorylation of Styrene

Palladium‐catalysed monophosphorylation of (R)‐2,2′‐bisperfluoroalkanesulfonates of BINOL (R^F=CF₃ or C₄F₉) by a diaryl phosphinate [Ar₂P(O)H] followed by phosphine oxide reduction (Cl₃SiH) then lithium diisopropylamide‐mediated anionic thia‐Fries rearrangement furnishes enantiomerically‐pure (R)‐2′‐diarylphosphino‐2′‐hydroxy‐3′‐perfluoralkanesulfonyl‐1,1′‐binaphthalenes [(R)‐ 8ab and (R)‐ 8g–j ], which can be further diversified by Grignard reagent (RMgX)‐mediated CF₃‐displacement [→(R)‐ 8c–f ]. Coupling of (R)‐ 8a–j with (S)‐1,1′‐binaphthalene‐2,2′‐dioxychlorophosphine (S)‐ 9 generates 3′‐sulfonyl BINAPHOS ligands (R,S)‐ 10a–j in good yields (43–82%). These new ligands are of utlility in the asymmetric hydrophosphonylation of styrene ( 1 ) by 4,4,5,5‐tetramethyl‐1,3,2‐dioxaphospholane 2‐oxide ( 2 ), for which a combination of the chiral ligands with either [Pd(Cp)(allyl)] or [Pd(allyl)(MeCN)₂]⁺/NaCH(CO₂Me)₂ proves to be a convenient and active pre‐catalyst system. A combination of an electron‐rich phosphine moiety and an electron‐deficient 3′‐sulfone moiety provides the best enantioselectivity to date for this process, affording the branched 2‐phenethenephosphonate, (−)‐iso‐ 3 , in up to 74% ee with ligand (R,S)‐ 10i , where Ar=p‐anisyl and the 3′‐SO₂R group is triflone.     

Discovery of 3‐Hydroxy‐3‐phenacyloxindole Analogues of Isatin as Potential Monoamine Oxidase Inhibitors

A series of 3‐hydroxy‐3‐phenacyloxindole analogues of isatin were designed, synthesized, and evaluated in vitro for their inhibitory activity toward monoamine oxidase (MAO) A and B. Most of the synthesized compounds proved to be potent and selective inhibitors of MAO‐A rather than MAO‐B. 1‐Benzyl‐3‐hydroxy‐3‐(4′‐hydroxyphenacyl)oxindole (compound 18 ) showed the highest MAO‐A inhibitory activity (IC₅₀: 0.009±0.001 μm , K_i: 3.69±0.003 nm ) and good selectivity (selectivity index: 60.44). Kinetic studies revealed that compounds 18 and 16 (1‐benzyl‐3‐hydroxy‐3‐(4′‐bromophenacyl)oxindole) exhibit competitive inhibition against MAO‐A and MAO‐B, respectively. Structure–activity relationship studies suggested that the 3‐hydroxy group is an essential feature for these analogues to exhibit potent MAO‐A inhibitory activity. Computational studies revealed the possible molecular interactions between the inhibitors and MAO isozymes. The computational data obtained are congruent with experimental results. Further studies on the lead inhibitors, including co‐crystallization of inhibitor–MAO complexes and in vivo evaluations, are essential for their development as potential therapeutic agents for the treatment of MAO‐associated neurological disorders.     

Synthesis and Cytostatic and Antiviral Activities of 2′‐Deoxy‐2′,2′‐difluororibo‐ and 2′‐Deoxy‐2′‐fluororibonucleosides Derived from 7‐(Het)aryl‐7‐deazaadenines

A series of sugar‐modified derivatives of cytostatic 7‐heteroaryl‐7‐deazaadenosines (2′‐deoxy‐2′‐fluororibo‐ and 2′‐deoxy‐2′,2′‐difluororibonucleosides) bearing an aryl or heteroaryl group at position 7 was prepared and screened for biological activity. The difluororibonucleosides were prepared by non‐ stereoselective glycosidation of 6‐chloro‐7‐deazapurine with benzoyl‐protected 2‐deoxy‐2,2‐difluoro‐D ‐erythro‐pentofuranosyl‐1‐mesylate, followed by amination and aqueous Suzuki cross‐couplings with (het)arylboronic acids. The fluororibo derivatives were prepared by aqueous palladium‐catalyzed cross‐coupling reactions of the corresponding 7‐iodo‐7‐deazaadenine 2′‐deoxy‐2′‐fluororibonucleoside 20 with (het)arylboronic acids. The key intermediate 20 was prepared by a six‐step sequence from the corresponding arabinonucleoside by selective protection of 3′‐ and 5′‐hydroxy groups with acid‐labile groups, followed by stereoselective S_N2 fluorination and deprotection. Some of the title nucleosides and 7‐iodo‐7‐deazaadenine intermediates showed micromolar cytostatic or anti‐HCV activity. The most active were 7‐iodo and 7‐ethynyl derivatives. The corresponding 2′‐deoxy‐2′,2′‐difluororibonucleoside 5′‐O‐triphosphates were found to be good substrates for bacterial DNA polymerases, but are inhibitors of human polymerase α.     

Synthesis and characterization of novel wholly para‐oriented aromatic polyamide‐hydrazides containing sulfone‐ether linkages

Four novel wholly para‐oriented aromatic polyamide‐hydrazides containing flexibilizing sulfone‐ether linkages in their main chains have been synthesized from 4‐amino‐3‐hydroxy benzhydrazide (4A3HBH) with either 4,4′‐sulfonyldibenzoyl chloride (SDBC), 4,4′‐[sulfonylbis(1,4‐phenylene)dioxy]dibenzoyl chloride (SODBC), 4,4′‐[sulfonylbis(2,6‐dimethyl‐1,4‐phenylene)dioxy]dibenzoyl chloride (4MeSODBC), or 4,4′‐(1,4‐phenylenedioxy)dibenzoyl chloride (ODBC) via a low‐temperature solution polycondensation reaction. A polyamide‐hydrazide without the flexibilizing linkages is also investigated for comparison. It was synthesized from 4A3HBH and terephthaloyl chloride (TCl) by the same synthetic route. The intrinsic viscosities of the polymer ranged from 2.85 to 4.83 dL g^?1 in N,N‐dimethyl acetamide (DMAc) at 30°C and decreased with introducing the flexibilizing linkages into the polymer. All the polymers were soluble in DMAc, N,N‐dimethyl formamide (DMF), and N‐methyl‐2‐pyrrolidone (NMP), and their solutions could be cast into films with good mechanical strengths. Further, they exhibited a great affinity to water sorption. Their solubility and hydrophilicity increased remarkably by introducing the flexibilizing linkages. The polymers could be thermally cyclodehydrated into the corresponding poly(1,3,4‐oxadiazolyl‐benzoxazoles) approximately in the region of 295–470°C either in nitrogen or in air atmospheres. The flexibilizing linkages improve the solubility of the resulting poly(1,3,4‐oxadiazolyl‐benzoxazoles) when compared with poly(1,3,4‐oxadiazolyl‐benzoxazoles) free from these linkages. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Studies on polyurethanes and polyurethane–ureas derived from divalent metal salts of mono(hydroxybutyl) hexolate

Divalent metal salts of mono(hydroxybutyl)hexolate [M(HBH)₂), M=Ca²⁺, Mn²⁺or Pb²⁺] were synthesized by the reaction of 1,4‐butanediol, 5,6,7,8,10,10‐hexachloro‐3a,4,4a,5,8,8a,9,9a‐octahydro‐5,8‐methanonaphtho‐[2,3‐C]‐furan‐1,3‐dione and divalent metal acetates. Hexamethylene bis [N′‐(1‐hydroxy‐2‐methyl‐prop‐2‐yl)urea] (HBHMPU) and tolylene 2,4‐bis[N ′‐(1‐hydroxy‐2‐methyl‐prop‐2‐yl)urea] (TBHMPU) were synthesized by reacting 2‐amino‐2‐methyl‐propan‐1‐ol with hexamethylene diisocyanate (HMDI) and tolylene 2,4‐diisocyanate (TDI), respectively, in toluene solvent. Flame‐retardant metal‐containing polyurethanes were synthesized by the solution polymerization of HMDI with M(HBH)₂ and the polyurethane–ureas by reacting HMDI with 1:1 mixture of M(HBH)₂ and HBHMPU or TBHMPU, respectively, in DMSO as solvent. The polymers have been characterized by elemental analysis, solubility, viscosity and IR and ¹H NMR spectroscopy. The thermal stability of the polymers has been studied by thermogravimetry. The flame‐retardant property of the polymers has been investigated by measuring limiting oxygen index values. © 2000 Society of Chemical Industry