Starch derivatives of high degree of functionalization 9: carboxymethyl starches

This paper describes the synthesis of carboxymethyl starch (CMS) ID various alcohols (methanol, ethanol, isopropyl alcohol) as slurry media and with different starch types. The products were investigated regarding their degree of substitution (DS), their reaction efficiency (RE), and their pattern of functionalization. The highest DS obtained ID a one-step procedure was 1.40 with a RE of 82%, applying isopropyl alcohol as slurry medium. Moreover, by using the synthesis concept via a reactive microstructure, CMS samples with high DS values can be achieved ID a one-step synthesis as well. A multi-step carboxymethylation ID methanol, on the other hand, leads to maximal DS values of 2.3 after 10 conversions, dependent on the amylose content of the starch. ¹H NMR spectroscopic investigations show a reactivity ID the order O-2 > O-6 O-3 for the samples prepared ID alcoholic slurry media. ID contrast, the CMS synthesized via reactive microstructure reveals a preferred substitution ID position 6 and a non-statistic distribution of the carboxymethyl groups along the chain. A significant amount of 2,3,4,6-tetra--functionalization, caused by the branched structure of starch, was found.     

Influence of fluorinated substituent and terminal length on phase behavior of mesogen‐jacketed liquid crystalline polymers with a biphenyl mesogen

A series of mesogen‐jacketed liquid crystalline polymers, poly{2,2,3,3,4,4,4‐heptafluorobutyl 4′‐hydroxy‐2‐vinylbiphenyl‐4‐carboxylate} (PF3Cm, where m is the number of carbon atoms in the alkoxy groups, and m = 1, 4, 6, and 8), the side chain of which contains a biphenyl core with a fluorocarbon substituent at one end and an alkoxy unit of varying length on the other end, were designed and successfully synthesized via atom transfer radical polymerization. For comparison, poly{butyl 4′‐hydroxy‐2‐vinylbiphenyl‐4‐carboxylate} (PC4Cm), similar to PF3Cm but with a butyl group instead of the fluorocarbon substituent, was also prepared. Differential scanning calorimetric results reveal that the glass transition temperatures (T_gs) of the two series of polymers decrease as m increases and T_gs of the fluorocarbon‐substituted polymers are higher than those of the corresponding butyl‐substituted polymers. Wide‐angle X‐ray diffraction measurements show that the mesophase structures of these polymers are dependent on the number of the carbon atoms in the fluorocarbon substituent and the property of the other terminal substituent. Polymers with fluorocarbon substituents enter into columnar nematic phases when m ≥ 4, whereas the polymer PF3C1 exhibits no liquid crystallinity. For polymers with butyl substituents, columnar nematic phases form when the number of carbon atoms at both ends of the side chain is not equal at high temperatures and disappear after the polymers are cooled to ambient temperature. However, when the polymer has the same number of carbon atoms at both ends of the side chain, a hexagonal columnar phase develops, and this phase remains after the polymer is cooled. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Pharmacologically interesting compounds—I: High resolution mass spectra of phenothiazines

The mass spectra of twenty-six commercially available medicinal phenothiazines have been determined at high resolution. In each compound, the side chain attached to the 10-position of the phenothiazine ring contains nitrogen and fission of the C? C bond α to this nitrogen gives in most cases the base peak. Some of the compounds are also substituted at the 2-position and this substituent generally remains intact, though some substituents such as acetyl, propionyl, methoxyl and methylthio can undergo fragmentation. Fragmentations fall into three groups; those which give ions representing a part of the side chain; those which give ions representing the intact phenothiazine ring with part of the side chain attached; those which give ions representing a partially fragmented ring system.     

A novel class of platelet activating factor (PAF) antagonists. I. Synthesis and structure-activity studies on PAF-sulfonamide isosteres.

New platelet activating factor (PAF) antagonists, 3 were synthesized by replacing the charged phosphate and trimethylammonium moieties with sulfonamide and heterocyclic quaternary ammonium functionalities, respectively (PAF-sulfonamide isosteres). Darmstoff phosphatidic acid analogues of this class (Darmstoff-sulfonamide isosteres), 6 were also synthesized. The activity of these compounds as PAF antagonists was evaluated from their in vitro inhibitory effect on PAF-induced platelet aggregation in rabbit platelet-rich plasma. Among the compounds tested, some of the 2-methoxypropane derivatives with an octadecylcarbamoyloxy or octadecylcarbamoylthio side chain at the 1-position and a propylsulfonamide function bearing a terminal polar substituent such as a quaternary quinolinium or substituted quinolinium group at the 3-position were found to be the most potent (IC50 = 0.3-0.6 microM).     

Synthesis of water soluble 8-substituted 5-deazaflavins

By oxidative cyclization of 5,5′-arylmethylenebis(6-methylaminouracil) derivatives with diethyl azodicarb-oxylate a number of 5-deazaisoalloxazines were synthesized having at the C(8) position a substituent that causes a bathochromic shift varying between 20 and 130 nm, depending on the substituent. To increase the solubility in aqueous media 8-substituted 5-deazaflavins were prepared having a carboxymethyl group at the N(3) position. The carboxymethyl group was introduced prior to the oxidative cyclization.     

Transmission of electronic substituent effects through cage polycyclic alkanes: a computational study of diamantane derivatives based on structural variation

The transmission of long-range polar effects (field effects) across the diamantane cage has been investigated by analyzing the small structural changes induced by a variable substituent X in the phenyl group of 9-substituted 4-phenyldiamantane derivatives. The structures of many such molecules with charged or dipolar substituents have been determined from quantum chemical calculations at the HF/6-31G* and B3LYP/6-311++G** levels of theory. Comparison with the results of a similar study carried out on 4-substituted 1-phenylbicyclo[2.2.2]octane derivatives, where the distance between probe and substituent is substantially smaller, shows that the ability of the diamantane framework to transmit field effects is 45 % of that of the bicyclo[2.2.2]octane framework when X is a dipolar, uncharged substituent. This figure increases to 59 % in the case of charged groups. The structural results support the idea that the field effect of a dipolar substituent attenuates more rapidly with distance than that of a charged group. This makes it impossible to construct a single, universal scale of field parameters including both dipolar and charged groups. A single scale can only be set up for a fixed separation between substituent and probe. The presence of the variable substituent X has a pronounced effect on the geometry of the diamantane cage. The nonbonded distance between the bridgehead carbons C4 and C9 spans an interval about 0.20 Å wide and correlates quite well with the mean value of the three cage angles at C9. These geometric changes are closely similar to those of the corresponding parameters in 4-substituted 1-phenylbicyclo[2.2.2]octane derivatives. The concerted structural variation of the polycyclic cage is controlled primarily by the group electronegativity of X and does not correlate with the much smaller structural variation of the phenyl probe.     

Comprehensive analysis of the substitution pattern in dextran ethers with respect to the reaction conditions

Dextrans from Leuconostoc ssp., α-1,6-linked glucans branched at O-3, were O-methylated in DMSO with lithium dimsyl and methyl iodide under various conditions. Methyl substituent distribution was comprehensively studied in the terminal, internal, and branched glucosyl units and along and over the dextran macromolecules. The order of reactivity was O-2 > O-4 ≥ O-3. The methyl pattern in the glucosyl units significantly deviates from a random distribution with enhanced amounts of un- and trisubstituted moieties. This deviation was found to proceed on macromolecular level by means of ESI-MS of perdeuteromethylated and partially depolymerized methyl dextrans. Heterogeneity was much more pronounced than for methyl amylose prepared under comparable conditions. DS gradients in and over the material are discussed with respect to dextran structure and the mechanism of Li dimsyl alkylation. For comparison, cyanoethyl dextrans were prepared by sodium hydroxide catalyzed addition of acrylonitrile. Monomer analysis of cyanoethyl dextrans revealed that this thermodynamically controlled reaction gave a random substitution pattern with 48% of cyanoethyl groups at O-2, 33% at O-4, and 19% at O-3.      

Pyridyl groups for protection of the imide functions of uridine and guanosine. Exploration of their displacement reactions for site-specific modifications of uracil and guanine bases

For the protection of the O-4 function of uridine and the O-6 of guanosine, 2-, 3- and 4-hydroxypyridines, 2-pyridinethiol, 6-methyl-2-hydroxy- and 6-methyl-3-hydroxypyridines have been employed. These substituted pyridines gave pyridyl-N-and/or pyridyl-O-substituted derivatives, depending both upon the position of the hydroxyl and methyl groups in the pyridine ring, at the C-4 and the C-6 of the uracil and guanine residues, respectively. These groups were found to be good leaving groups for nucleophilic substitution reactions by amines, thiolates and oximate. If needed, the rate of these substitution reactions could be conveniently increased by almost 1000-fold by conversion of the pyridyl moiety to its methiodide.     

Syntheses of Chalcone‐Type Chlorophyll Derivatives Possessing a Bacteriochlorin,Chlorin or Porphyrin π‐System and Their Optical Properties

C3‐(Trans‐2‐arylethenyl)carbonylated chlorophyll derivatives possessing a bacteriochlorin or chlorin π‐system were synthesized by cross‐aldol (Claisen–Schmidt) condensation of methyl pyrobacteriopheophorbide‐a or 3‐acetyl‐3‐devinyl‐pyropheophorbide‐a bearing the C3‐acetyl group with p‐(un)substituted benzaldehydes under basic conditions. The corresponding porphyrin‐type chlorophyll derivatives were prepared by the oxidation (17,18‐didehydrogenation) of the chlorin‐type. Their Qy absorption and fluorescence emission maxima in dichloromethane correlated well with Hammett substituent constants of the p‐substituents. Several electron‐withdrawing p‐substituents suppressed the emission due to photoinduced electron transfer quenching in a molecule. The substitution sensitivities for their maxima and fluorescence quantum yields decreased in the order of bacteriochlorin‐, chlorin‐ and porphyrin‐type derivatives.     

Bent-core liquid crystals with a 2-substituted 3-hydroxybenzoic acid central core

We report the synthesis and study of the mesomorphic behaviour for a series of bent-core materials based on 2-substituted 3-hydroxybenzoic acid as a central unit. Properties of the studied compounds are tuned by lateral substitution (F, Cl, CH₃, NO₂ and CN) in the position 2 of 3-hydroxybenzoic acid and by the length of the terminal alkyl chain. All studied homologues exhibit at least one mesophase. Mesomorphic properties are established and compared with other 3-hyhroxybenzoic derivatives studied previously, with analogous orientation of ester linkages, laterally substituted at different position on the central core. The role of the substitution and the length of the terminal alkyl chain are discussed.     

The eosin-sensitized photooxidation of substituted phenylalanines and tyrosines.

Abstract— The eosin-sensitized photooxidation of tyrosine and a number of compounds related to tyrosine (substituted phenylalanines) was studied by steady-state kinetic and flash photolysis techniques. In particular, the role of the phenolic group and the amino and carboxyl groups of the alanyl side chain in the photooxidation mechanism was investigated in detail. Several relationships between substrate structure and susceptibility to photooxidation as well as effects of substrate structure on photooxidation mechanisms were found. For example, phenylalanine is not photooxidizable, hut substitution of electron-donating (activating) groups such as-OH (as in tyrosine) or-NH₂ (as in p-aminophenylalanine) results in rapidly photooxidized derivatives. However, substituting deactivating groups such as—C1 (as in p-chlorophenylalanine) or weakly activating groups such as - OCH₃ (as in 4-methoxyphenylalanine) result in non-photooxidiz-able derivatives. Substitution of additional activating groups to the ring of hydroxy-substituted phenylalanines results in increased rates of photooxidation, whereas additional deactivating groups result in decreased photooxidation rates. The rate-determining step in the photooxidation mechanism is shown to be dependent on the presence and position of an electron-donating substituent on the benzenoid ring. Only minor involvement of the side chain amino and carboxyl groups was found. Both singlet oxygen and hydrogen abstraction mechanisms are involved in the eosin-sensitized photooxidation of hydroxy-substituted phenylalanines (e.g. tyrosine). The hydrogen abstraction mechanism probably predominates at both pH 8 and 11.     

Preparation and chromatographic evaluation of β-cyclodextrin derivative CSPs bearing substituted phenylcarbamate groups for HPLC

Five β-cyclodextrin (β-CD) derivatives bearing substituted phenylcarbamate/3-(triethoxysilyl)propylcarbamate groups at the 2-, 3-, and 6-positions of glucose unit and another five derivatives containing benzoate at the 2-position and substituted phenylcarbamate/3-(triethoxysilyl)propylcarbamate groups at the 3- and 6-positions were synthesized using the regioselective esterification method. The obtained β-CD derivatives were efficiently immobilized onto the silica gel through the intermolecular polycondensation of a small amount of the triethoxysilyl groups, which were used as the chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC). The chiral separation properties of these CSPs were evaluated under the normal-phase HPLC. The effects of solvent polarity and the side chain structures of β-CD derivatives on the chiral recognition ability of the immobilized CSPs were investigated. Among these β-CD derivative CSPs, 2,3,6-tris(3,5-dichlorophenylcarbamate)-β-CD CSP showed a relatively high chiral recognition ability for the studied racemates. The regioselective esterification at the 2-position of glucose unit in the β-CD decreased the chiral recognition ability at the same conditions. For some racemates, the β-CD derivative CSPs showed chiral recognition abilities comparable or better to some chemical bonded β-CD derivative CSPs and 3,5-dichloro- and 3,5-dimethylphenylcarbamates of cellulose and amylose CSPs.     

Efficient, one-pot transformation of indoles into functionalized oxindole and spirooxindole systems under Swern conditions

The reaction of indole derivatives bearing a 3- or 4-hydroxyalkyl chain with dimethylsulfoxide and oxalyl chloride under Swern conditions led to a one-pot, three-component process involving three different synthetic transformations, namely oxidation of indole to oxindole, introduction of a chlorine substituent at the oxindole C-3 position and substitution of the hydroxyl group in the side chain by chlorine, in good to excellent overall yields. The same conditions, applied to a 2-methylindole, afforded a 2-formylindole derivative oxidized at its side chain. The reaction starting from one indole with a 2-hydroxyalkyl chain furnished 3-(2-hydroxyalkyl)oxindoles. Finally, application of the Swern conditions to derivatives of indole-3-propionic or -butyric acid afforded 3-spirooxindole lactones.     

Preparation,characterization, and mesophase formation of esters of ethylcellulose and methylcellulose

A range of mixed ether-esters of cellulose was prepared from partially substituted ethylcellulose and methylcellulose. The ¹³C-NMR analysis of ethylcellulose with a DS of 2.5 indicated that the hydroxyl groups at carbon six of anhydroglucose units were completely substituted. Acetylation of the ethylcellulose under different conditions yielded (acetyl) (ethyl) cellulose (AEC) samples with acetyl degree of substitution ranging from 0 to 0.5. Fully substituted (propionyl) (ethyl) cellulose (PEC) and (acetyl) (methyl) cellulose (AMC) were also prepared. Chiral nematic liquid crystals were formed in these mixed ester/ethers of cellulose in concentrated solutions of acidic solvents. The critical concentration for the phase separation of the cellulosic solutions depended on the nature of the substituent, the degree of substitution, and the solvent at a given temperature. Methylcellulose solutions in trifluoroacetic acid and dichloroacetic acid form chiral nematic liquid crystals with a left-handed helicoidal structure. The acetylated methyl cellulose samples did not show the reversal of handedness with increasing acetyl content that was previously observed for the corresponding ethylcellulose samples. © 1994 John Wiley & Sons, Inc.     

Synthesis and chiral recognition of novel amylose derivatives containing regioselectively benzoate and phenylcarbamate groups

A new class of regioselectively substituted amylose derivatives bearing three different substituents at 2-, 3- and 6-positions, and two different substituents at 2-position and 3-, 6-positions were synthesized by a sequential process based on the esterification of 2-position of a glucose unit. Their chiral recognition abilities were evaluated as chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC). Each derivative had its own characteristic recognition ability depending on the arrangement of side chains at the three positions. Among the derivatives, amylose 2-(4-t-butylbenzoate) and amylose 2-(4-chlorobenzoate) series exhibited high chiral recognition. Some racemates can be efficiently separated on these derivatives as well as on the amylose tris-3,5-dimethylphenylcarbamate, which is commercially available as Chiralpak AD and one of the most powerful CSPs. The structures of the amylose derivatives were also investigated by circular dichroism spectroscopy.     

Nitration of Pyrrolo[1,2-<Emphasis Type="Italic">a</Emphasis>]pyrazines

We have synthesized nitro derivatives of pyrrolo[1,2-a]pyrazines using a nitrating mixture and acetyl nitrate. We have obtained the products of oxidation of the side chain of 1,6-substituted pyrrolo[1,2-a]-pyrazines. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1579–1586, October, 2005.     

Aromatic nucleophilic substitution. Part 2. Preparation of novel 3-substituted xanthone and thioxanthone derivatives

The novel 3-nitro-9-oxo-9H-xanthene- and 3-nitro-9-oxo-9H-thioxanthene-l-carboxylic acids 2a–d were prepared by intramolecular acylation of 3-aryloxy- and 3-arylthio-5-nitrophthalic anhydrides 1 (Scheme). The 3-nitro group was readily substituted by O- and S-nucleophiles and halide and azide ions to give a range of 3-substituted thioxanthone derivatives 3 with varied λ_max.     

The synthesis and reactions of 4-(2- and 3-thienyl)-tetrahydroisoquinolines

Tetrahydroisoquinoline derivatives substituted in the 4-position by either a 2- or 3-substituted thiophene ring have been synthesised. Simple electrophilic substitution reactions of these systems take place as expected in the α-position of the thiophene ring. Metalation reactions are more complex and take place at the benzylic 4-position of the tetrahydroisoquinoline nucleus in the case of the 2-substituted thiophene derivatives or at either the thiophene α-positions or the benzylic 4-position depending on the nature of the attacking electrophile in the case of the 3-substituted thiophene system.     

FUNCTIONAL POLYMERS 65. SYNTHESIS AND BRIEF CHARACTERIZATION OF SURFACE ACTIVE 2(2-HYDROXYPHENYL)2H-BENZO-TRIAZOLE ULTRAVIOLET STABILIZERS

A number of 2(2-hydroxyphenyl)2H-benzotriazoles substituted in the 5-position with reactive hydroxyl and carboxyl groups have been synthesized. They include compounds with a tert butyl substitution in the 3-position or without substitution. The latter compounds were subjected to a reaction with N-hydroxy-methyl-(meth)acrylamide to form acrylic polymerizable 3(meth)acrylamidomethyl-2(2-hydroxyphenyl)2H-benzotriaz-oles. Hydroxyl reactive compounds were allowed to react with long chain acids, compounds with carboxyl groups with long chain hydrocarbon, fluorocarbon or silicon oligomer alcohols. The polymerizable 2(2-hydroxyphenyl)2H-benzotriazoles were then copolymerized with methyl methacrylate. Films made from such polymers showed by contact angle measurements, substantial migration of the fluorocarbon or silicon component to the surface of the film.     

4-(1-Haloalkyl)-3-nitrotetrahydrofurans as versatile scaffolds for the synthesis of diversely functionalized tetrahydrofurans

4-(1-Haloalkyl)-3-nitrotetrahydrofurans, which are accessible by tandem oxidative oxa-Michael addition/radical cyclization/ligand transfer reactions, can be processed to diversely substituted tetrahydrofuran derivatives. Selective epimerization at the nitro function provides tetrahydrofuran diastereomers, which cannot be prepared by the tandem process. Intramolecular alkylations furnish interesting bridgehead nitro oxabicyclo[3.1.0]hexane derivatives in high yields. Intermolecular substitution reactions of the halide functions succeed only with nucleophiles, which are not basic enough to trigger intramolecular alkylations. The aryl substituent in 2-aryl-3-nitrotetrahydrofurans can be selectively oxidatively transformed to carboxylic acid derivatives using catalytic Ru(III) and NaIO₄ without affecting the nitro group. Reduction and hydrogenation reactions provide differently substituted 3-aminotetrahydrofuran derivatives depending on the conditions with moderate to good chemoselectivity.