Showing papers by "Angelo C. Pinto published in 1998"
TL;DR: In this paper, a simple, high yielding, methodology for the N-alkylation of substituted isatin derivatives using calcium hydride in DMF is described, and a simple and high yielding methodology for Nalkylated isatin derivative is presented.
67 citations
TL;DR: The bark of Croton cajucara afforded two novel clerodane-type furano-diterpenes, t-cajucarin B and sacacarin, which were obtained by spectroscopic measurements including 2D-NMR experiments.
66 citations
TL;DR: In this paper, the crude oil of Copaifera cearensis was subjected to flash chromatography on KOH-impregnated silica gel from which three fractions were obtained: hexane, dichloromethane and methanol fractions.
27 citations
TL;DR: In this article, the underivatized acetone and hexane fractions from propolis samples (predominant flora Citrus spp. and Vernonia polyanthes) were analyzed by HT-HRGC (high temperature high resolution gas chromatography) coupled to mass spectrometry.
Abstract: The underivatized acetone and hexane fractions from propolis samples (predominant flora Citrus spp. and Vernonia polyanthes) were analyzed by HT-HRGC (high temperature high resolution gas chromatography) and HT-HRGC coupled to mass spectrometry (HT-HRGC-MS). Several compounds, including flavonoid aglycones, phenolic acids, and high molecular weight compounds were characterized in crude extracts by HT-HRGC-MS. HT-HRGC and HT-HRGC-MS were shown to be quick and informative tools for rapid analysis of crude extracts without need for prior derivatization and purification.
24 citations
TL;DR: A short glass capillary column coated with PS-090 (20% phenyl-80% methylpolysiloxane, of 10 m × 030 mm id; with 1 μm film thickness) was used to analyze samples from Tephrosia candida; eighteen rotenoids were separated and identified without derivatization by HT-HRGC and HTHRGC-MS.
Abstract: A short glass capillary column coated with PS-090 (20% phenyl–80% methylpolysiloxane, of 10 m × 030 mm id; with 01 μm film thickness) was used to analyze samples from Tephrosia candida; eighteen rotenoids were separated and identified without derivatization by HT-HRGC and HT-HRGC-MS The mass spectra show the typical fragmentation pattern for rotenoids, with the base peaks either at M+, or originating from RDA (Retro Diels-Alder) rearrangements HT-HRGC and HT-HRGC-MS were shown to be extremely valuable and neglected techniques for structural studies as well as the routine analysis of rotenoids in crude extracts Possible applications to other classes of aromatic natural products, eg flavonoids, are envisaged
16 citations
TL;DR: In this paper, the scientific career of Theodor Peckolt, naturalist and pharmacist, and his seminal contribution to the development of phytochemistry in Brazil are discussed in the light of the historical background of the Brazilian science and University at his time.
Abstract: In this paper we briefly describe the scientific career of Theodor Peckolt, naturalist and pharmacist, and his seminal contribution to the development of phytochemistry in Brazil. His achievements are discussed in the light of the historical background of the Brazilian science and University at his time.
16 citations
TL;DR: The natural products chemistry of the gorgonian Lophogorgia punicea, collected on the Southeast Brazilian coast, were investigated for the first time Gas chromatography - mass spectral analysis of the monohydroxylated sterol mixture revealed the presence of nine common C26 to C29 cholestane derivatives as mentioned in this paper.
Abstract: The natural products chemistry of the gorgonian Lophogorgia punicea, collected on the Southeast Brazilian coast, were investigated for the first time Gas chromatography - mass spectral analysis of the monohydroxylated sterol mixture revealed the presence of nine common C26 to C29 cholestane derivatives A detailed study of the crude extract of Lophogorgia punicea led to the isolation of hydroquinone and a new polyhydroxylated sterol named punicin (1) The structure of punicin was determined by interpretation of spectral data including 2D NMR and HRFABMS Punicin is an unprecedented sterol possessing a C-17 hydroxyl group, a feature uncommon in marine organisms
13 citations
TL;DR: In this article, a mixture of two monoisoprenylated flavonols velloquercetin 3,3,4,4′-dimethyl ether (Vellozia graminifolia) was isolated and characterized from the hexane whole plant extract.
12 citations
TL;DR: In this article, a complete assignment of the signals in the 1H and 13C NMR spectra and the stereostructural analysis of the compounds prepacifenol epoxide and the new dehydroxyprepacifenola epoxide are presented.
Abstract: A complete assignment of the signals in the 1H and 13C NMR spectra and the stereostructural analysis of the compounds prepacifenol epoxide and the new dehydroxyprepacifenol epoxide are presented. These compounds were extracted from the marine mollusc Aplysia dactylomela and represent the first occurrence of chamigrenes found in Brazilian waters. The NMR analyses are supported by NOE difference and COSY experiments and also by gradient selected HMBC, HSQC-TOCSY and HSQC-DE. 1H spectra simulations were done for the final fitting of the chemical shifts and coupling constants.
9 citations
4 citations