Claudio C. Lopes

Total syntheses of oxygenated brazanquinones via regioselective homologous anionic Fries rearrangement of benzylic O-carbamates

Using new variations of anionic aromatic chemistry, the total synthesis of oxygenated brazanquinones (1a-1c), derived from β-brasan, a natural product isolated from Caesalpina echinata, via carbamates 2a-2c is described.

Synthesis of Dimethoxyfuranonaftoquinones

Abstract Recently some furanonaphthoquinones were isolated from Tabebuia species2,3,4. The structures la, lb2, and li4 were assigned to three of these compounds (those of la and lb being later confirmed by synthesis3,5,6). However, for the three other isolated compounds the spectroscopic data did not permit a decision to be made between the 2,3,4 - - - 4 isomeric pairs of structure lc and Id, le and lf 3, and lg and lh 4. Compounds la, lb, and le (or If), were tested in the KB cell culture assay and shown to be more active cytotoxic agents than lapachol2,3, the probable biogenetic precursor of all of them.

Eugenol and safrole as starting materials for the synthesis of 3-alkyl muconic acid mono and dimethyl esters and 4,4-dialkyl butenolides

Abstract Compounds 1b-e and 2b-d prepared from eugenol ( 1a ) and safrole ( 2a ) respectively were submitted to ozonation in methanol at 0°C. The 3-alkyl muconic acid dimethyl esters 4b-e were produced from 1b-e (∼ 45%), while starting from 2b-d the 3-alkyl muconic acid monomethyl esters 6b-d were obtained regiospecifically (∼ 75%). These latter compounds were transformed (∼ 85%) into the 4,4-dialkyl butenolides 7b-d .

STUDY OF THE PROTONATION/DEPROTONATION SEQUENCE OF TWO POLYAMINES: BIS-[(2S)-2-PYRROLIDINYLMETHYL] ETHYLENEDIAMINE AND SPERMIDINE BY 1H AND 13C NUCLEAR MAGNETIC RESONANCE

ABSTRACT In this paper we describe the study of protonation/deprotonation of two polyamines: bis-[(2S)-2-pyrrolidinylmethyl]ethylenediamine (tetra) and spermidine (Spd). A new synthetic route was established for the synthesis of tetra, which structure was confirmed by IR, elemental analyzes, 1H-NMR, 13C-NMR(Pendant) and 2D-NMR (COSY, 13C-1H HETCOR and HMQC) spectra. The protonation/deprotonation sequence studies of tetra and Spd were determined by potentiometric and NMR methods. For the NMR studies, the tetra and Spd samples were dissolved in D2O and the pD adusted with NaOD. The protonation/deprotonation sequences of tetra and Spd were determined by means of the values and the variations of the hydrogen atom and 13C NMR chemical shifts as a function of hydrogen atom pD. The variation of δ 1H with pD clearly showed that the first protonation of tetra occurs at the pyrrolidine nitrogen atoms and the second protonation occurs at the ethylenediamine nitrogen atom. The analysis of the 13C-NMR spectra confirmed the results obtained by 1H-NMR, as a greater chemical shift variation was observed for C-6 (5.6 ppm), as compared to C-8 (1.8 ppm). In the study with Spd, the greater chemical shift variation was observed for C-2 (6.75 ppm) and C-5 (4.95 ppm), indicating that the deprotonation occurs first at the secondary nitrogen atoms and the second and third deprotonation steps occur at the primary nitrogen atoms.

Vanillin (1) As Starting Material for the Synthesis of Isomeric Phthalides

Abstract Phthalides have bcen employed as useful intcriucdiates in tic sqrnthcsis of my condcnscld aromatic carbocyclic and heterocyclic compounds, including several natural products In this paper we report two alternative synthetic pathways for the preparation of phthalides as shown for the synthesis of the isomeric pairs of compounds 5a-d and 7a-d.

Identification of source of a marine oil-spill using geochemical and chemometric techniques.

The current work aimed to identify the source of an oil spill off the coast of Maranhão, Brazil, in September 2005 and effect a preliminary geochemical survey of this environment. A combination of bulk analytical parameters, such as carbon isotope (δ(13)C) and Ni/V ratios, and conventional fingerprinting methods (High Resolution Gas Chromatography and Mass Spectrometry) were used. The use of bulk methods greatly speeded source identification for this relatively unaltered spill: identification of the likely source was possible at this stage. Subsequent fingerprinting of biomarker distributions supported source assignment, pointing to a non-Brazilian oil. Steranes proved the most useful biomarkers for sample correlation in this work. Distribution patterns of environmentally more resilient compound types, such as certain aromatic structures, proved inconclusive for correlation, probably in view of their presence in the background.

Straightforward synthesis of 2,2,4,4,5,7,7-d7-cholestane: a new deuterated standard in petroleum analysis

A short and efficient synthesis of heptadeuterated 2,2,4,4,5,7,7-d7-cholestane (1) from cholesterol (3) is described. The deuterated material will be useful for the analysis of different sources of petroleum in analytical geochemistry laboratories as internal standard for quantification of steranes via gas chromatography-mass spectrometry (GC-MS).

Preliminary study of insect attraction by a mixture of semiochemicals containing 1,2,4-Trimethoxybenzene in domestic citric-culture

In this work we describe a new efficient strategy for the preparation of 1,2,4-trimethoxybenzene (3) in 56% overall yield. The compound 3 was used in a preliminary study of insect attraction by a mixture of semiochemicals called TIV, composed of indol (1), vanillin (2) and 1,2,4-trimethoxybenzene (3), in eight Mc Phail style traps installed at a domestic orchard of citric-culture, containing 120 trees not infected by plagues in Bom Jesus Farm, located next to a patch of the Atlantic Forest, at Silva Jardim, Rio de Janeiro, Brazil.

Synthesis of 1,2,4-Trimethoxybenzene and Its Selective Functionalization at C-3 by Directed Metalation

Abstract A new and efficient strategy was developed for the preparation of 1,2,4-trimethoxybenzene (3, a powerful attractant of Euglossini bees) and its C-3 derivatives (7a–j), from vanillin (2) in 56% overall yield.

UMA NOVA SÍNTESE DE α-BROMO-ACETOFENONAS E SUA APLICAÇÃO NA OBTENÇÃO DE 2-BENZOIL- BENZOFURANAS

a-Bromoacetophenones are important in organic synthesis. They have been widely used as precursors of several natural products. Several methods of bromination aiming at their synthesis have been described, however they furnish a mixture of starting material 10, mono 8 and dibromide 11 products. We developed a novel, simple and efficient synthesis of these compounds with applications in the synthesis of benzoylbenzofurans 9, compounds with important pharmacological properties, such as the ability of dilating the coronary artery and analgesic action. Such compounds have also been used as key intermediates to obtain quinone systems.