Synthesis Of Model Compounds Research Articles

Algal Carotenoids. 55. Structure Elucidation of (3S,5R,6R,3'S,5'R,6'S)-13'-cis-7',8'-Dihydroneoxanthin-20'-al 3'-beta-D-Lactoside (P457). Part 1. Reisolation, Derivatization and Synthesis of Model Compounds.

Algal Carotenoids. 55. Structure Elucidation of (3S,5R,6R,3'S,5'R,6'S)-13'-cis-7',8'-Dihydroneoxanthin-20'-al 3'-beta-D-Lactoside (P457). Part 1. Reisolation, Derivatization and Synthesis of Model Compounds.

Synthesis of Model Compounds of Safflomin C

Abstract 3-[3,3-Dimethyl- and 3-hydroxy-3-methyl-2,4-dihydroxy-5-(4-hydroxycinnamoyl)-6-oxo-1,4-cyclohexadienyl]- 3-(4-hydroxyphenyl)propanoic acid were synthesized as model compounds of safflomin C. Their spectra closely resembled that of safflomin C.

Chlorotrifluoroethylene-derived fluids. I. Model compound synthesis

A series of chlorofluoroalkanes having chlorines on adjacent carbon atoms has been prepared, i.e. n-C 5F 11CFClCCl 3, n-C 6F 13CFClCCl 3, n-C 5F 11CFClCFCl 2, n-C 6F 13CFClCFCl 2, n-C 5F 11CFClCF 2Cl, n-C 2F 5CFClCFClC 3F 7 and n-CF 3CFClCFClC 4F 9, by a combination of halogen exchange, dehalogenation and chlorine addition reactions. An attempt to synthesize n-C 6F 13CFClCF 2CFCl 2 by the coupling of n-C 6F 13CFClI with an excess of ICF 2CFCl 2 under UV radiation in the presence of Hg gave only n-C 6F 13CFClCFClC 6F 13 together with CFCl 2CF 2CF 2CFCl 2. Under parallel conditions from n-C 6F 13CFClI and CF 2ClCFClI, n- C 6F 13CFClCFClCF 2Cl was obtained in 48% yield.

Derivate natürlicher Tetrapyrrole, Synthese einiger Modellverbindungen für die Photodynamische Therapie

Natural Tetrapyrrol Derivatives, Synthesis of Some Model Compounds for the Photodynamic TherapyIn photodynamic therapy, di‐ and polymeric porphyrins with ether, ester or direct CC linkages are the active components of hematoporphyrin derivative. Here we describe the synthesis of some new model compounds for such ether/ester dimers.

A short synthesis of 1,3,4,6-tetra- O-acetyl-2-azido-2-deoxy-β- d-glucopyranose and the corresponding α-glucosyl chloride from d-mannose

2-Acetamido-2-deoxy-D-glucopyranose is a constituent of many biologically important glycoconjugates. Chemical syntheses of model compounds related to these substances require glycosyl donors which favor the formation of either 1,2-cis or 1,2-tram glycosidic linkages. Glycosyl donors derived from 2-amino-2-deoxy-D-ghrcose that show a P-directing effect in the glycosylation reaction are relatively easily accessible’; more difficult to obtain are their a-directing counterparts. The 2-azido glycosyl halide approach is the most useful means for the stereoselective synthesis ofthe a-glycosidic linkage in the aminosugar series. According to this strategy’, the nonparticipating azido group is positioned at C-2 of the requisite monosaccharide, which is then converted into a glycosyl halide. After glycosylation, the azido group can be readily converted into a 2-amino or 2-acylamino function. According to the existing method?‘, however, the preparation of the precursors of glycosyl halide derivatives of 2-azido-2-deoxy-D-glucose is a tedious, multistep process. This, to a considerable extent, is because logical precursors such as the C-2 sulfonate derivatives of methyl cr-D-mannopyranoside do not undergo S,2 displacement reactions easily6,‘, and therefore cannot be used as intermediates to efficiently synthesize the corresponding 2-azido-2-deoxy-D-glucose derivatives. If an efficient inversion of the D-WZaW’Z0 to D-g/uco configuration is to be achieved by the S,2 displacement of a suitable leaving group, then the reaction should be carried out with a (usually less accessible) derivative ofg-D-mannose7. Recent critical evaluation” of the available routes to the precursors of glycosyl halides of 2-azido-2-deoxyhexoses found the azidonitration method’ most advantageous. That procedure, however, requires resolution of a complex mixture of products by chromatography. This laboratory has recently reported’ that treatment of 1,3,4,6-tetra-O-acetyI_PD-mannopyranose (1) with diethylaminosulfur trifluoride (DAST) afforded the corre-

The structure and partial synthesis of imbricatine, a benzyltetrahydroisoquinoline alkaloid from the starfish Dermasterias imbricata

The structure of imbricatine (1), a cytotoxic metabolite of the starfish Dermasterias imbricata, has been determined by spectroscopic analysis and chemical degradation. Synthesis of model compounds 7 and 18 provided evidence for the absolute configuration and constitution of the benzyltetrahydroisoquinoline substructure of imbricatine. Key words: imbricatine, asteroid, alkaloid.

C NMR Spectroscopic Studies of Phenylcoumaran and 1,2-DiarylpropaneType Lignin Model Compounds Part 1. Synthesis of Model Compounds

Article C NMR Spectroscopic Studies of Phenylcoumaran and 1,2-DiarylpropaneType Lignin Model Compounds Part 1. Synthesis of Model Compounds was published on January 1, 1991 in the journal Holzforschung (volume 45, issue s1).

Model compound synthesis for the structure determination of new unknown planar aromatic compounds originating from pulp mill

Several model compounds have been synthesized for verification of the structures of new unknown planar aromatic compounds (UPACs) observed in high-resolution gas chromatography/low-resolution mass spectrometry analyses of the polychlorodibenzodioxins (PCDDs) and polychlorodibenzofurans (PCDFs) in pulp mill products, effluents, sediments and mussels. The mass spectra of synthetic alkyl polychlorodibenzofurans (C 6-PCDFs) were different, but those of alkyl polychlorobibenzyls (C 5-PCBBs) were very similar compared to the spectra of UPACs.

Nucleophilic reactions of sorbic acid

The conjugated dienoic acid structure of sorbic acid renders it susceptible to nucleophilic attack. Nucleophiles known to react with sorbic acid include sulphite ion and amines. These attack the molecule in position 5 and, in the cse of amines, cyclization to form substituted dihydropyridones may follow. Recent investigations show that thiols in general can also add to sorbic acid. Cysteine, for example, reacts slowly with sorbic acid at 80 degrees C and pH 5.5, leading to 5-substituted 3-hexenoic acid. In general, reaction products are difficult to isolate from aqueous reaction mixtures as they are susceptible to acid- and base-catalysed hydrolysis. A synthesis of model compounds may be carried out by reaction of sorbate esters with the appropriate thiol (or its ester if it is an acid) in the presence of the corresponding sodium alkoxide. It is interesting that alkyl thiols give di-adducts with sorbate ester whilst low molecular weight thiols containing an oxygen atom give a monoadduct. The mechanism of this reaction and its implications to the preparation of samples for toxicological evaluation are discussed. The reaction of sorbic acid with nitrite ion is unusual and its mechanism is considered.

Structure of the Calystegines: New alkaloids of the nortropane family.

Three new alkaloids have been isolated from Calystegia sepium; their structures have been established from their 1H and 13C N.M.R. spectra, and confirmed by the synthesis of model compounds.

New m‐carborane‐containing polymeric schiff bases

AbstractNew soluble m‐carborane‐containing polymeric Schiff bases are prepared by polycondensation of m‐carboranylenediamine, 1,7‐bis(4‐aminophenylcarboxy)‐m‐carborane, and 1,7‐bis(4‐aminophenylamido)‐m‐carborane with different dialdehydes in solution. Optimum conditions for polymer synthesis are found. The structure of the resulting polymers is confirmed by the synthesis of model compounds not described earlier, IR spectroscopy, and elemental analysis data. Some properties of m‐carborane‐containing polymeric Schiff bases and their model compounds have been studied.

ChemInform Abstract: Selective Protection of Polyamines: Synthesis of Model Compounds and Spermidine Derivatives.

AbstractA general procedure for selective protection of mixed prim.‐sec.

The fluorescence of the chromophore of the green fluorescent protein of Aequorea and Renilla

A possible explanation for the lack of fluorescence in the isolated chromophore of the green fluorescent protein found in bioluminescent coelenterates has been provided by the synthesis of model compounds and a more satisfactory structure is suggested.

Selective protection of polyamines: synthesis of model compounds and spermidine derivatives

A general procedure for the selective protection of mixed primary-secondary (poly)amines, based on t-butoxycarbonylation of carbamate groups (exhaustive t-butoxycarbonylation) derived from the primary amino functions only, is reported. In most cases to be described, benzyl (poly)carbamates are used for this purpose. Subsequent removal of all benzyloxycarbonyl (Z) groups from the resulting intermediates by catalytic hydrogenolysis liberates the secondary amino functions, while t-butoxycarbonyl (Boc) is retained on the primary ones. Alternatively, selective removal of Z only from amino functions protected by both Z and Boc, which can be accomplished by base-catalysed methanolysis, results in protected (poly)amines with Boc and Z on their primary and secondary amino groups, respectively. The new reactions have been studied with two unsymmetrical derivatives of ethylene- and p-phenylene-diamine as model substances. The yields of most intermediates and the products were high. Additional experiments have been performed with spermidine to give N1,N8-Boc2-spermidine. Finally, by virtue of the non-equivalence of the two primary amino groups in this molecule, the synthesis of N8-Boc-N1-Z-spermidine by the same approach is presented.

Synthesis of model compounds of some biogenetic precursors of aflatoxin B1

The synthesis of analogues of various natural products occurring during the biosynthesis of the notorious hepatocarcinogen aflatoxin B1(1) is described. These natural products are versiconol (21), versiconol acetate (22), versicolorin C (23), versiconal acetate (4), and 4-[2,3-dihydroxy-1-(hydroxymethyl)propyl]-3,8-dihydroxy-1-methoxyxanthone (24). The synthesis of an analogue of versiconal (5) is also described.

Chemoselective acylation for the synthesis of model compounds of polynucleotide analogs

Synthese de N-pentyl-3(adenineyl-9)-2 propionamide et N-diethyl) adeninoyl-9)-2 propionamide. Preparation de poly(vinylamine-alcool vinylique) contenant des derives de la thymine optiquement actifs comme groupes lateraux greffes

Absolute stereochemistry of (+)-1,8a-dihydro-3,8-dimethylazulene, a labile biosynthetic intermediate for 1,4-dimethylazulene. Determination by theoretical calculation of CD spectra and verification by synthesis of model compounds

Absolute stereochemistry of (+)-1,8a-dihydro-3,8-dimethylazulene, a labile biosynthetic intermediate for 1,4-dimethylazulene. Determination by theoretical calculation of CD spectra and verification by synthesis of model compounds

Stereochemical evidence for participation of a Donor-acceptor complex in alternating copolymerization. 1. Model compound synthesis

Synthese stereospecifique d'une serie de composes modeles de copolymeres alternes maleimide N-substitue-ether vinylique. La stereochimie prodominante des unites succinimide dans les copolymeres est erythro

Identification of some bicyclic alkanes in petroleum

Bicyclic alkanes containing the drimane skeleton have been identified in crude oils and sediments by synthesis of model compounds. Two other bicyclic alkanes, whose skeletons do not conform to the isoprene rule, have also been identified from mass spectral data. A correlation between the relative concentration of C 29 steranes and diasteranes and drimane and two C 15 bicyclanes in an extensive sample suite, suggests a similar mechanism is involved in the formation of diasteranes and the two C 15 bicyclanes in the subsurface. The widespread occurrence of drimanes and drimane-related compounds in crude oils and sediments indicates that these compounds are derived from a ubiquitous source. The presence of methyldrimanes in a sample rich in methylhopanes suggests that drimanes and hopanes may be derived from similar precursors.

A New Synthesis of Model Compounds for the beta-5 Structural Unit in Lignins.

Synthese d'[hydroxy-4' methoxy-3' phenyl]-2 dihydro-2,3 benzofurannemethanol-3 a partir de benzyloxy-2 methoxy-3 benzaldehyde et de benzyloxy-4' methoxy-3' acetophenone