Difference between heartwood and sapwood
Forest Products Laboratory (U.S.)
1919
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The aim defined for this thesis consists on the synthesis of analogue compounds of
psoralen with dibenzofuran, carbazole and dibenzothiophene skeleton and on the
study of their antitumor activities against some human cancer cell lines.
The synthetic strategy used for the preparation of these analogues is based on
methods described in the literature for reactions of aromatic and heteroaromatic
compounds. The ultimate objective of these syntheses is the formation of the
pyranone by a reaction sequence that needs appropriate substrates for the cyclisation
to occur.
For the synthesis of some analogues o-hydroxyaldehydes as starting compounds are
required. Their preparations were carried out by Reimer-Tiemann formylation to
introduce the aldehyde group in an ortho position to the hydroxyl group. The
pyranone ring formation was pe...
O objectivo deste trabalho consistiu na síntese de N-glicopéptidos
fluorescentes com potencial actividade biológica.
Inicialmente preparou-se uma glucosilamina a qual foi ligada a corantes,
aminoácidos e a péptidos pela posição anomérica, originando uma ligação amida entre
o açúcar e o grupo carboxílico do composto a ligar.
Sintetizou-se o péptido Gly-Phe-Pro por síntese sequencial e foram ainda feitas
tentativas de preparação de um glicopéptido fluorescente por síntese convergente.
Como unidades fluorescentes utilizaram-se os corantes ácido 4-(nafto[1,2-d]
[1,2,3]triazol-2-il)benzóico e o ácido cumarina-3-carboxílico, anteriormente estudados
pelo nosso grupo de investigação, que foram ligados à glucosilamina, à glicina ou à
extremidade glicina do péptido Gly-Phe-Pro.
Foi realizada a desprotecção do açúcar ligado aos fluoróforos e tamb...
The synthetic methodology and experimental results concerning to the preparation of glycoconjugates bearing an amino acid unit or a heteroaromatic moiety will be discussed.
Descrece-se a obtenção de extractos de diferentes vegetais, plantas e frutos e estabelece-se, para cada um, a respectiva escala de pH.
The electrochemical intramolecular cyclisation of alfa-bromo propargyloxy (1 and 2) and allyloxy
(3) esters was carried out in ethanol and in ethanol–water mixtures as environmentally friendly
systems using Ni(II) complexes as the catalysts. The reduction of the substrates proceeds via
one-electron cleavage of the carbon–bromine bond to form a radical-type intermediate that
undergoes cyclisation to afford cyclic ethers in moderate to good yields.
The controlled-potential reduction of [1-bromo-2-methoxy-2-(prop-2'-ynyloxy)ethyl]benzene(1a), 1-[2-bromo-2-phenyl-1-(prop-2'-ynyloxy)ethyl]-4-methoxybenzene (1b) and 2-bromo-3-(3',4'-dimethoxyphenyl)-propargyloxypropanamide (1c) catalysed by
(1,4,8,11-tetramethyl-1,4,8,11 tetraazacyclotetradecane)nickel(I), [Ni(tmc)]+, at a vitreous carbon cathode in DMF/Et4NBF4 leads to 2-methoxy-4-methylene-3-phenyl-tetrahydrofuran (2a), 2-(4'-methoxyphenyl)-4-methylene-3-phenyl-tetrahydrofuran (2b) and 2-(3',4'-dimethoxyphenyl)-3-carbamoyl-4-methylenetetrahydrofuran (2c), respectively, in very high yields.
The electrochemical intramolecular cyclisation of propargyl 2-bromoethers 1-3 in N,N'-dimethylformamide at constant current in a diaphragmless cell has been developed using Ni(II) complexes as electron-transfer mediators. During controlled-current electrolyses of solutions of Ni(II) complexes in the presence of bromoethers, catalytic reduction of the latter proceeds via one-electron cleavage of the carbon–bromine bond to form a radical intermediate that undergoes cyclisation to afford the cyclic compounds in moderated to good yields.
The indirect electroreduction of unsaturated α-bromoesters using Ni(II) complexes as electron-transfer mediators is achieved in N,N'-dimethylformamide by constant current electrolysis between a cathode and a sacrificial anode in a diaphragmless cell. Cyclic compounds are obtained in moderate to good yields in conditions that avoid the usual preparation using organotin reagents.
The synthesis of some intermediates of furofuran lignans was accomplished by a chemical cyclisation reaction using N-ethylpiperidine hypophosphite and azobisisobutyronitrile. This reaction afforded the 5-exo-dig cyclic compound as the major product along with another isomeric cyclic compound which possess an endocyclic double bond.
A brief discussion is presented to explain the formation of these isomeric cyclic compounds by a base-catalysed tautomerism mechanism. Some structural aspects are discussed based on nuclear magnetic resonance data.
The indirect electroreduction of unsaturated aliphatic halides using Ni(II) complexes as electron-transfer mediators is achieved in N,N'-dimethylformamide by constant current electrolysis between a cathode and a sacrificial anode in a diaphragmless cell. Cyclic compounds are obtained in low to high yields in conditions that avoid the usual preparation using organotin reagents.
