Showing papers on "Substituent published in 1985"

Mechanisms of coenzyme B12-dependent rearrangements.

Abstract: Coenzyme B12 serves as a cofactor in various enzymatic reactions in which a hydrogen atom is interchanged with a substituent on an adjacent carbon atom. Measurement of the dissociation energy of the coenzyme's cobalt-carbon bond and studies of the rearrangement of model free radicals related to those derived from methylmalonyl-coenzyme A suggest that these enzymatic reactions occur through homolytic dissociation of the coenzyme's cobalt-carbon bond, abstraction of a hydrogen atom from the substrate by the coenzyme-derived 5'-deoxyadenosyl radical, and rearrangement of the resulting substrate radical. The only role thus far identified for coenzyme B12 in these reactions--namely, that of a free radical precursor--reflects the weakness, and facile dissociation, of the cobalt-carbon bond.

Reversible inhibitors of beta-glucosidase.

Abstract: A variety of reversible inhibitors of sweet almond beta-glucosidase were examined. These included simple sugars and sugar derivatives, amines and phenols. With respect to the sugar inhibitors and, indeed, the various glycoside substrates, the enzyme has what can be considered a "relaxed specificity". No single substituent on glucose, for example, is essential for binding. Replacement of a hydroxyl group with an anionic substituent reduces the affinity while substitution with a cationic (amine) substituent enhances the affinity. Amines, in general, are good inhibitors, binding more tightly than the corresponding alcohols: pKiRNH3+ = 0.645pKiROH + 1.77 (n = 9, r = 0.97). The affinity of a series of 10 primary amines was found to be strongly influenced by substituent hydrophobicity: pKi = 0.52 pi + 1.32 (r = 0.95). The major binding determinant of the glycoside substrates is the aglycon moiety. Thus, the Ki values of phenols are similar in magnitude to the Ks values of the corresponding aryl beta-glucoside. The pH dependence for the inhibition by various phenols indicates that it is the un-ionized phenol which binds to the enzyme when an enzymic group of pKa = 6.8 (+/- 0.1) is protonated. The affinity of the phenol inhibitor is dependent on its basicity with a Bronsted coefficient for binding of beta = -0.26 (n = 14, r = 0.98). The pH dependence of the binding of two particularly potent beta-glucosidase inhibitors was also examined. 1-Deoxynojirimycin (1,5-dideoxy-1,5-imino-D-glucitol) has a pH-corrected Ki = 6.5 microM, and D-glucono-1,5-lactam has a pH-corrected Ki = 29 microM.(ABSTRACT TRUNCATED AT 250 WORDS)

The chemistry and biochemistry of C-nucleosides and C-arylglycosides.

Abstract: Publisher Summary This chapter reviews recent advances in the chemistry and biochemistry of C-nucleosides, the literature concerning C-arylglycoside (i.e., nonnitrogen heterocyclic C-nucleoside) antibiotics, and recent significant advances in the synthesis of C-nucleosides and C-glycosides. It also discusses biological test data and data that are relevant to structure–activity relationships. Modification of readily available natural C-nucleosides is an attractive route to new C-nucleoside analogs and derivatives, because one starting material often possesses much of the desired functionality and chiral properties. The chapter illustrates this approach with examples. The most frequently used strategy for C-nucleoside synthesis involves the construction of a heterocyclic aglycone from the C-1 substituent of a functionalized sugar intermediate.

Nematogenic polymers having rigid chains. 1. Substituted poly(p-phenylene terephthalates)

Abstract: Influence des substituants Cl, Br, C 6 H 5 et C 6 H 13 sur la temperature de transition de ces polymeres

Silver halide photographic material

Abstract: PURPOSE:To obtain a coupler capable of controlling in a wide range and independently of a coupling reaction rate and liberating rate of a photographically useful group from a timing group by using a specified coupler. CONSTITUTION:In the coupler having a cleavable group by the reaction with an oxidized product of a developing agent, the cleavable group is expressed by the formula, wherein L is -X-CR1R2-, or -O-CO-; X is O, S, or tert. amino; R1 and R2 express H or a substituent, or R1 may form a ring by combining with R2; L may be bonded to TIME with a carbon atom. Preferred substituent for R1 and R2 is such as halogen, alkyl, alkenyl, aralkyl, aralkenyl, aryl, or heterocyclic residue. TIME is a timing group, and PUG is a photographically useful group.

Substituent effects on the electronic structure of metalloporphyrins: a quantitative analysis in terms of four-orbital-model parameters

Abstract: The effects of substituents at the periphery of the porphyrin ring on its a - a* absorption spectrum are determined in a quantitative fashion by using a new approach based on the four-orbital model. To accomplish this we systematically investigated with UV-visible absorption spectroscopy the Mg (Sn), Zn, Cu, Ni, and Pt series of metals incorporated into porphyrins with different substituents at the periphery of the macrocycle. The metal dependence of the UV-visible spectrum is used to determine relative energy splittings of the frontier orbitals, intensity parameters for a - a* transitions, and configuration interaction energies for metalloporphyrins with a variety of patterns of peripheral substitution (P, OEP, UroP, CoproP, ProtoP, and TPP). Differences in these MO parameters for distinct porphyrins are related to inductive and conjugative effects of the substituents. In particular, a good correlation between the splitting of the Lu-band and the Soret band for a series of copper porphyrins and the Hammett constants for the substituents is explained by a relationship between the electron-withdrawing ability of substituents and the strength of the configuration interaction that mixes one-electron excited states of the porphyrin. Variations among the porphyrins in the configuration interaction energy result from delocalization of ring charge caused by increased mixing of p-orbitals of the substituent a-carbons with ring orbitals as the "electronegativity" of the substituents increases. Delocalization of ring charge onto substituent carbons lowers the electron-electron repulsion, and therefore the configuration interaction. Anomalous features of the spectra of the metalloporphines and metalloprotoporphyrins are also explained. The spectra of the metalloporphines are unusual because suitable substituent p-orbitals are not available on the hydrogens for mixing with ring a-orbitals. The spectra of the metalloprotoporphyrins are of biological interest and are found to be only mildly anomalous. The unusual features can be traced to enhanced mixing with and delocalization of ring charge onto the a-system of the two vinyl substituents. For a complete understanding of substituent effects on the absorption spectra, changes in the configuration interaction, orbital energies, and transition dipoles must all be considered.

Anti-inflammatory/anti-allergic compounds

Abstract: Compounds of the formula: and salts thereof, wherein Ar 1 is a nitrogen, sulfur, oxygen heterocyclic ring or aromatic ring; Ar is a phenyl ring or a nitrogen, oxygen or sulfur heterocyclic ring; Ar and Ar 1 may be fully substituted or less than fully substituted with H, CH 3 , lower alkyl, aryl, aralkyl, halo, hydroxy, lower alkoxy, CF 3 , carboxy, alkylcarboxy, arylcarboxy, alkylcarbalkoxy, alkanoyl, formyl, oxo, nitrilo, amino, aminoalkyl, alkylamine, carboxamide, aryloxy, nitro, sulfonyl, sulfonamide, thio, or alkylthio; X = -O(CHR 1 ) n -, , -NR 2 (CHR 1 ) n -alkylene of up to 2 carbon atoms in the principal chain and up to a total of 4 carbon atoms, Z is an alkylene chain containing up to 10 carbon atoms in the principal chain and a total of up to 12 carbon atoms and from 0 to 2 double bonds and the said alkylene chain may be attached to Ar through an oxygen, sulfur or amino nitrogen atom, and when n'= 2 , one of the R substituents may be halogen on an omega carbon of the alkylene chain Z; when n'=1, R is a substituent attached to one of the carbon atoms of Z selected from the group consisting of =0, OR 3 , SR 3 , N(R 2 ) 2 and R,, -COR 4 and when n'=2 one R is previously defined and the additional R is a substituent attached to one of the carbon atoms of Z selected from the group consisting of =O, OR 3 , SR a , N(R 2 ) 2 , -COR 4 , lactone and halo; R 1 is H or CH 3 ; R 2 is H, lower alkyl, aryl or aralkyl; R 3 is H, lower alkyl, lower alkanoyl, aryl, aralkyl or substituted aryl in which the substituent is halo, lower alkyl or lower alkoxy; R 4 is OR 2 or N(R 2 ) 2 ; n = 0 or 1; n' = 1 to 7; and n" = 0, 1 or 2. 2. A compound of the formula: and salts thereof, wherein Ar 1 is quinolyl; Ar is a phenyl, pyridyl or quinolyl ring; X = -O(CHR 1 ) n -, -, NR 2 (CHR 1 ) n -, alkylene of up to 2 carbon atoms in the principal chain and up to a total of 4 carbon atoms,

Vitamin D3 derivatives having a substituent at 2-position

Abstract: A 1α-hydroxy vitamin D3 derivative of the formula: ##STR1## where R1 is a hydroxyl group, an amino group or the group: OR' (where R' is a lower alkyl group having 1 to 7 carbon atoms that may or may not be substituted by a hydroxyl group, a halogen atom, a cyano group, a lower alkoxy group having 1 to 3 carbon atoms, an amino group, or an acylamino group); R2 is a hydrogen atom or a hydroxyl group), and a process for preparing the same are disclosed. The compound represented by the formula above has the calcium control action and the ability to induce differentiation in tumor cells and, therefore, are useful as an antitumor agents and a medicine for treating calcium dysbolism-caused diseases.

The distortion of the ring in monosubstituted benzene derivatives: a molecular orbital study

Abstract: Ab initio calculations using the 6-31G basis set have been carried out on benzene and the monosubstituted derivatives with CH3, NH2, OH, F, NO, CHCH2, CCH, CCF COO− O−, and with NO2, CHO, CHNH, COOH, CFO, CN, NC and NH3+, as substituent groups. The C- and H-atoms of the ring and the substituent group atom directly attached to it were assumed to lie in the same plane, and a particular orientation was assumed for certain groups, otherwise full geometry optimization was employed. Trends in the following parameters are discussed — the ipso angle, the lengths of the CC bonds which include the ipso angle, the CC and CH bond lengths, nonbonded C ⋯ C and H ⋯ H distances, the ring area, and the tilt of the unsymmetrical substituent groups with respect to the ring axis. Additional calculations at the 6–31G* level on benzene and the F, CN and NH2 derivatives show the trends to be unaffected by the inclusion of polarization functions on the heavy atoms. In selected cases the calculated geometries are compared with microwave and X-ray diffraction results. Comparison is also made with the Mulliken population analysis of Hehre, Radom and Pople (1972) who used the STO-3G basis set and standard geometry. The difference in energy between that for the optimized structure and that for a reference structure with optimized benzene ring geometry and the optimized geometry for the attachment and substituent group has been calculated for the F, NO2, OH, CN, CHCH2 and O− derivatives. The small values, less than 1 kcal mol−1, except for O−, suggest that the actual physical state might well be a mixture of structures having slightly different ring geometries.

Effects of replacement of a double bond by a cyclopropane ring in phosphatidylethanolamines: a 2H NMR study of phase transitions and molecular organization.

Abstract: The thermotropic behavior and molecular properties of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) and 1-palmitoyl-2-dihydrosterculoyl-sn-glycero-3-phosphoethanolamine (PDSPE) have been investigated by 2H NMR spectroscopy using samples selectively labeled at the 5'-, 9'-, 10'-, and 16'-positions of the sn-2 chains. Comparison with the corresponding phosphocholine analogues (POPC and PDSPC), obtained as intermediate synthetic products, was used to monitor the role of the polar head group. Replacement of the choline moiety by ethanolamine increased the gel to liquid-crystal transition temperature by 10-32 degrees C and led to a significantly higher ordering of the fatty acyl chains in the liquid-crystalline bilayer state. The lateral compression effect, due to the smaller area per polar head group in PE, results in a bilayer to hexagonal phase transition at elevated temperatures. The effects on both PC and PE due to replacement of the olefinic group by a cyclopropane unit are similar. A decrease in the temperature of the gel to liquid-crystal phase transition, Tc, is observed upon introduction of a cyclopropane ring; it goes from 26 degrees C in POPE to approximately 10 degrees C in PDSPE. In addition, a very significant broadening of the transition profile is observed. These observations are consistent with the poor packing ability of mixed saturated and cyclopropane-containing chains due to the bulky substituent effect. The temperature of the bilayer-hexagonal phase transition of PE samples was decreased by 15-20 degrees C on replacement of oleoyl chains by dihydrosterculoyl chains at the sn-2 position.(ABSTRACT TRUNCATED AT 250 WORDS)

Potential neuroleptic agents. 3. Chemistry and antidopaminergic properties of substituted 6-methoxysalicylamides.

Abstract: A series of substituted 6-methoxysalicylamides were synthesized from their corresponding 2,6-dimethoxybenzamides by demethylation of one methoxy group with boron tribromide. Substituted 6-methoxysalicylamides having a lipophilic aromatic substituent in the 3-position para with respect to the methoxy group, e.g. a bromo or an iodo atom or an ethyl or a propyl group, and having an (S)-N-(1-alkyl-2-pyrrolidinyl)methyl moiety as the side chain were found to be potent blockers of [3H]spiperone binding in vitro and potent inhibitors of the apomorphine syndrome in the rat. Similar to remoxipride but in contrast to haloperidol, some of the substituted salicylamides show a 10-20-fold separation between the dose that inhibits hyperactivity and that which inhibits stereotypy. It was concluded that, besides the requirement of a lipophilic substituent in the position para to the methoxy group for antidopamine activity in vivo, the formation of a coplanar six-membered pseudoring involving the amide moiety and the methoxy group is a structural requirement for activity in vitro.

An equation utilizing empirically derived substituent constants for the prediction of vicinal coupling constants in substituted ethanes

Abstract: A simple equation has been developed for the prediction of vicinal coupling constants in HCCH fragments: The equation is a cosine series in θ, the torsion angle between vicinal hydrogens. The feature which distinguishes this equation from similar equations is the inclusion of δSi terms, which describe the magnitude of each substituent's effect. These substituent constants have been defined from experimental data. An orientation effect which is dependent on the torsion angle(s) between substituent(s) and a vicinal hydrogen is included. Substituent constants have been defined for 39 groups, of which 15 have been experimentally determined herein. The parameters for the equation have been defined from 49 torsion angles in 19 conformationally rigid compounds. The torsion angles have been determined from x-ray crystal structure data and molecular mechanics calculations. The multiplicity of structures used to determine the substituent constants should allow for the application of this equation to a wide variety of structures.

Siloxane polyphotoinitiators of the substituted acetophenone type

Abstract: An organopolysiloxane photoinitiator having an average of at least two siloxane units, of which at least an average of one siloxane unit per organopolysiloxane molecule has the formula: X.sub.a R.sub.b SiO(.sub.4-a-b)/2 (I) wherein a is an integer of 1-3, b is an integer of 0-2 and a plus b equals 1-3; R is C 1 -C 10 hydrocarbyl or halogen substituted C 1 -C 10 hydrocarbyl; and X is a substituted acetophenone photomoiety selected from: ##STR1## where R 1 is any substituent which will not interfere with hydrosilation, n is an integer between 0 and 5 in formulas (II), (IIa), (III), (IIIa), (IV) and (IVa) and between 0 and 4 in formula (III) and (IIIa); m is 0 or 1; R 2 is alkyl or substituted alkyl; R 3 is H, alkyl or aryl; R 4 is a divalent hydrocarbon group having between 2 and 10 carbon atoms or an alkylene oxy alkylene group; R 5 is a group selected from H, alkyl, aryl, organosilyl, or the reaction product of an isocyanate esterification reagent or an etherification reagent with the hydroxyl product formed when R 5 is H and R 6 is a trivalent hydrocarbon or hydrocarbon oxyhydrocarbon group. The silicones are prepared by hydrosilation of the corresponding olefinically or acetylenically unsaturated acetophenones.

Substituent effects on benzylic radical hydrogen hyperfine coupling constants. Part 4. The effect of branching of the alkyl substituent

Abstract: The effects of substituents in the meta and para positions of the benzyl radical on the α-hydrogen hyperfine coupling constants (hfc's) are discussed. The electron spin resonance (esr) spectra of t...

Organogermane homopolymers and copolymers with organosilane

Abstract: The first high molecular weight soluble, formable organogermane homopolymer (n-Bu2Ge)n was synthesized by the sodium coupling of n-Bu2GeCl2 in toluene. Soluble organogermane/organosilane copolymers [(X2Ge)x(YZSi)y]n were prepared by sodium coupling of X2GeCl2 and YZSiCl2 in different molar ratios (X = n-bu, Ph; Y = n-hexyl, cyclohexyl; Z = Me). Germanium-containing polymers and copolymers with organosilanes are highly absorbing between 300–360 nm, with the absorption maxima dependent on the nature of the substituent and the ratio of X2Ge:YZSi in the polymer. These polymers are photoactive and display bleaching behavior with photoscission.

1,8-naphthyridine derivatives

Abstract: Novel 1,8-naphthyridine derivatives having antibacterial activity and represented by the following general formula (I): wherein: R is a cyclic amino group which may have a substituent; and X is a halogen atom, and their pharmacologically acceptable salts and a process for their preparation are disclosed

The chemistry of heteroarylphosphorus compounds. Part 16. Unusual substituent effects on selenium-77 nuclear magnetic resonance chemical shifts of heteroaryl- and aryl-phosphine selenides. X-Ray crystal structure of tri(2-furyl)phosphine selenide

Abstract: Crystals of PR3Se (R = 2-furyl) are monoclinic, space group Cc, with a= 11.720(6), b= 12.527(9), c= 8.569(5)A, and Z= 4. The structure was solved using multisolution direct methods and refined by least squares to R 0.038 (R′ 0.041) for 1 030 observed diffractometer data. Phosphorus adopts a distorted tetrahedral geometry with mean Se–P–C and C–P–C angles of 114.9 and 103.4°, respectively. The molecule has almost ideal C3 symmetry. The C–P–C angle is the smallest reported for a tertiary phosphine selenide. The average P–C bond length [1.778(6)A] and the P–Se bond length (2.094 A) are both considerably shorter than found in other arylphosphine selenides. The oxygen atoms of the 2-fury1 groups are arranged about the selenium atom, with an average Se ⋯ O distance of 3.577 A. 77Se N.m.r. studies show that the selenium atom is shielded by 86 p.p.m. compared with that in triphenylphosphine selenide, implying a ‘through-space’ interaction involving the 2-fury1 oxygen atoms. Selenium-77 chemical shifts have also been determined for a range of heteroaryl-and substituted phenyl-phosphine selenides. Whereas the 2-furyl group causes the selenium to become shielded, the related 2-thienyl group causes it to become deshielded. Deshielding of selenium is also experienced on introduction of ortho substituents in arylphosphine selenides. Thus, for example, the selenium atom of tris(2,4,6-trimethoxyphenyl)phosphine selenide is deshielded by 240 p.p.m. compared with that in triphenylphosphine selenide. Possible origins of these effects are considered.

Experimental and theoretical study of electronic substituent effects in 4-aminoaryl (4-substituted aryl) sulphones

Abstract: Substituent effects on the electronic structure of 23 biologically active 4-aminoaryl (4-substituted aryl) sulphones were investigated by means of 1H nmr, 13C nmr, and ir spectroscopy, as well as by semiempirical all-valence CNDO/2 calculations, with and without sulphur d orbital participation Good linear intercorrelations were found among the spectral data and between these and the computed electronic charges and the Hammett σp values On this basis the substituent effects are interpreted in terms of electronic charge perturbation, which is linearly transmitted from the substituent to the whole molecule, bridging SO2 group included The agreement between experimental and theoretical data is good and the trends do not depend on the inclusion or exclusion, in the calculations, of the sulphur d orbitals Strong and linearly related σ–π electron interactions operate between C-1 and C-1′ in the C(1)SO2C(1′) moiety; thus Koch and Moffitt's qualitative π-electron conjugation model for Case 2 type sulphones seems inadequate

Hydroxyphenyltriazines, process for their preparation and their use as UV absorbers

Abstract: Compounds of the formula in which at least one of the substituents R1 and R2 is a radical of the formula in which M is a cation, m is 1 or 2, R4 is alkyl or alkoxy each having 1 to 4 carbon atoms, hydroxyl or a radical of the formula -COR in which R denotes alkyl having 1 to 8 carbon atoms or denotes phenyl, and n is 0, 1, 2 or 3, and the other substituent or the other substituents independently of one another is or are alkyl, aryl or alkyl or aryl bonded to the triazinyl radical via a heteroatom, or is or are a heterocycle, are highly suitable as UV absorbers in organic materials.

Substituent effects on hydrogenation of aromatic rings: hydrogenation vs. hydrogenolysis in cyclic analogs of benzyl ethers

Abstract: Le fait de placer un benzylether dans un systeme cyclique semble retarder de facon importante l'hydrogenolyse par rapport aux analogues acycliques

Pyrazolo(1,5-B)-1,2,4-triazole derivatives

Abstract: A novel pyrazolo[1,5-b]-1,2,4-triazole derivative represented by the general formula (I) is described. ##STR1## wherein R 1 and R 2 which may be the same or different, each represents a hydrogen atom or a substituent; X represents a hydrogen atom or a group capable of being released upon coupling; and Y represents a hydrogen atom or an aralkyl group.