References of "Warin, Roger"
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See detailHourglass chondrules
Warin, Roger; Hatert, Frédéric ULg; Kashuba, John

in Meteorite (2011), November 2010

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See detailGuianensine, a zwitterionic alkaloid from Strychnos guianensis
Quetin-Leclercq, Joëlle; Llabres, Gabriel ULg; Warin, Roger et al

in Phytochemistry (1995), 40(5), 1557-1560

The isolation and structure determination of an alkaloid isolated from the stem bark of Strychnos guianensis is described. Elucidation of its structure is based mainly on 1D and 2D NMR studies. The new ... [more ▼]

The isolation and structure determination of an alkaloid isolated from the stem bark of Strychnos guianensis is described. Elucidation of its structure is based mainly on 1D and 2D NMR studies. The new alkaloid has a zwitterionic asymmetrical bis-indole structure and is named guianensine. [less ▲]

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See detailAnionic polymerization of acrylic monomers. 13. Carbon-13 NMR characterization of the mixed complexation of methyl α-lithioisobutyrate by lithium tert-butyoxide in tetrahydrofuran
Wang, Jin-Shan; Jérôme, Robert ULg; Warin, Roger et al

in Macromolecules (1994), 27(24), 1691-1696

The mixed complexation of methyl alpha-lithioisobutyrate(MIBLi)(a monomeric model structurally corresponding to the living end of PMMA-Li+) with lithium tert-butoxide (LiOtBu) in THF has been studied for ... [more ▼]

The mixed complexation of methyl alpha-lithioisobutyrate(MIBLi)(a monomeric model structurally corresponding to the living end of PMMA-Li+) with lithium tert-butoxide (LiOtBu) in THF has been studied for the first time by using C-13 NMR spectroscopy. It is shown that LiOtBu, like LiCl, is very effective in coordinating with MIBLi tetramer in THF, incrementally replacing MIBLi with the formation of other tetrameric complexes, MIBxLi4(OtBu)4-x (x = 1-3). Complextion of MIBLi by LiOtBu induces a shielding C-13 shift of the MIBLi C(alpha) resonance, which might suggest that lithium cations associated with the electron-rich ligands, i.e., LiOtBu, can also form weaker bonds with the carbonyl oxygen of MIBLi (i.e., mu-type complexes), thereby decreasing the localization of the negative charge on that latter atom. In comparison with LiCl, one of the most significant features is that only one single type of species results from mixed complexation of MIBLi and LiCl at LiCl/MIBLi = 1, 2, and greater-than-or-equal-to 3, respectively, at low temperature, whereas several LiOtBu-complexed species may coexist, whatever the LiOtBu/MIBLi ratio; furthermore, their exchange is found to be very slow at a temperature as high as 0-degrees-C. Tentatively, this striking feature may explain nicely the large difference in molecular weight distribution of poly(meth)acrylates anionically prepared in the presence of LiOtBu and LiCl, respectively. [less ▲]

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See detail2,7-dihydroapogeissoschizine from root bark of strychnos Gossweileri
Quetin-Leclercq, Joëlle; Dive, Georges ULg; Delaude, Clément et al

in Phytochemistry (1994), 35(2), 533-536

In this paper, we describe the isolation and structural determination of 2,7-dihydroxyapogeissoschizine, a new alkaloid from the root bark of Strychnos gossweileri. Elucidation of its structure is based ... [more ▼]

In this paper, we describe the isolation and structural determination of 2,7-dihydroxyapogeissoschizine, a new alkaloid from the root bark of Strychnos gossweileri. Elucidation of its structure is based mainly on 1D and 2D NMR studies; its conformation was optimized by energy minimization. This type of skeleton is related to geissoschizine but with the notable diffrence that the 1 and 17 positions are joined giving an additional fused ring. Such a seven-membered ring has ,to our knowledge, only been observed in apogeissoschizine, obtained after chemical tratment of two alkaloids ( geissospermine and geissoschizine). 2,7-dihydroxyapogeissoschizine is therefore, the first natural product possessing this skeleton. According to a preliminary test, this new alkaloid shows low toxicity to B16 melanoma cells, but not for non-cancer 3T3 fibroblasts cultured in vitro.THese results have to be confirmed by further tests. [less ▲]

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See detailAnionic polymerization of (meth)acrylic monomers. 12. Efect of lithium chloride on the stereochemistry on the anionic polymerization of methyl methacrylate in THF and in a 9/1 toluene/THF mixture
Wang, Jin-Shan; Jérôme, Robert ULg; Warin, Roger et al

in Macromolecules (1993), 26(22), 5984-5990

The effect of LiCl on the stereochemistry of the anionic polymerization of methyl methacrylate in the presence of a lithium counterion at -78-degrees-C in THF and in a 9/1 toluene/THF mixture, has been ... [more ▼]

The effect of LiCl on the stereochemistry of the anionic polymerization of methyl methacrylate in the presence of a lithium counterion at -78-degrees-C in THF and in a 9/1 toluene/THF mixture, has been studied by C-13 and H-1 NMR spectroscopy. It has been found that LiCl has an important effect on the E/Z ratio of the living chain ends in THF, in contrast to the main-chain tacticity. In contrast, LiCl has a significant influence on the stereoregularity of the anionic polymerization of MMA in a 9/1 toluene/THF mixture. When the LiCl/initiator molar ratio is increased, the syndiotactic placements (rr) are favored at the expense of the isotactic ones (mm). This effect can be accounted for by a multistate propagating mechanism controlled by association/complexation equilibria among associated, nonassociated, and LiCl-complexed species. These association/complexation equilbria, which were originally proposed by Muller, appear to have a decisive effect not only on the livingness (molecular weight distribution (MWD)) but also on the stereochemistry of the anionic polymerization of MMA in a 9/1 toluene/THF mixture at -78-degrees-C, confirming the involvement of the ligand in propagation control. [less ▲]

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See detailProanthocyanidins from Ribes nigrum 1 Isolation and structure determination
Tits, Monique ULg; Angenot, Luc ULg; Warin, Roger et al

Poster (1992, May)

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See detailRevision of the structure of strychnofluorine
Quetin-Leclercq, Joëlle; Warin, Roger; Delaude, Clément et al

in Journal de Pharmacie de Belgique (1992), 47(3), 242

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See detailProanthocyanidins from Ribes nigrum leaves - Isolation and structure determination
Tits, Monique ULg; Angenot, Luc ULg; Warin, Roger et al

in Bulletin de Liaison Groupe Polyphenols (1992)

In summary, the antiinflammatory activity of Ribes nigrum leaves is mainly due to proanthocyanidins which are the major oligomers in the proanthocyanidins fraction

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See detailRevision of the structure of strychnofluorine, an alkaloid of Strychnos gossweileri
Quetin-Leclercq, Joëlle; Coune, Claude; Delaude, Clément et al

in Phytochemistry (1992), 31(12), 4347-4349

The structure of strychnofluorine, an indole alkaloid isolated in 1980 from the root bark of Strychnos gossweileri, has been revised. Strychnofluorine proved to be identical with 18 ... [more ▼]

The structure of strychnofluorine, an indole alkaloid isolated in 1980 from the root bark of Strychnos gossweileri, has been revised. Strychnofluorine proved to be identical with 18-hydroxynorfluorocurarine that has been isolated as a minor (contaminated) alkaloid from Strychnos ngouniensis in 1983. [less ▲]

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See detailMatadine, a cytotoxic alkaloid from Strychnos gossweileri
Quetin-Leclercq, Joëlle; Coucke, P.; Delaude, Clément et al

in Phytochemistry (1991), 30(5), 1697-1700

Matadine, a new alkaloid, has been isolated from the root bark of Strychnos gossweileri. Elucidation of its structure is mainly based on 1H and 1D NMR studies. Its cytotoxic activity has been tested on ... [more ▼]

Matadine, a new alkaloid, has been isolated from the root bark of Strychnos gossweileri. Elucidation of its structure is mainly based on 1H and 1D NMR studies. Its cytotoxic activity has been tested on cancer cells and normal cells. Matadine is an anhydronium base as serpentine, that exerts also a selective inhibiting activity on B16 melanoma cells while it is less toxic in human 2002 non-cancer cells. This selective activity might be well due , as it seems to be the case for serpentine and alstonine, to a higher affinity of matadine for destabilized single-stranded DNA as mainly present in cancer cells. [less ▲]

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See detailRevision of the Structure of Strychnochromine
Quetin-Leclercq, Joëlle; Angenot, Luc ULg; Dupont, Léon et al

in Tetrahedron Letters (1991), 32(34), 4295-4298

The structure of strychnochromine, an unusual alkaloid isolated from a new batch of the root bark of Strychnos gossweileri has been revised . To confirm the indoline structure ( proposed in 1988) and to ... [more ▼]

The structure of strychnochromine, an unusual alkaloid isolated from a new batch of the root bark of Strychnos gossweileri has been revised . To confirm the indoline structure ( proposed in 1988) and to establish the stereochemistry of the compound extensive 2D-NMR experiments were carried out. The COSY experiments mostly confirmed the previous observations but the COLOC maps did not fit the first proposed structure!The problem was solved by single-crystal X-ray analysis of the p-bromobenzoyl ester of strychnochromine. The new structure, with its tetrahydroquinoline ring, is very unusual in Strychnos species but the formation of quinolines from indole alkaloids has already mentioned in some other plants ( Cinchona, Alstonia, Hunteria..). [less ▲]

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See detailProanthocyanidins from Ribes nigrum leaves 1. Isolation and structure determination
Tits, Monique ULg; Angenot, Luc ULg; Warin, Roger et al

Poster (1990, July)

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See detailAn indolinic cryptoalkaloid from Strychnos mattogrossensis
Angenot, Luc ULg; Belem-Pinheiro, Maria-Lucia; Imbiriba da Rocha, Arnaldo et al

in Phytochemistry (1990), 29(8), 2746-2749

A new indolinic cryptoalkaloid, mattogrossine, has een isolated from the roots and branches of Strychnos mattogrossensis collected near Manaus. Elucidation of its structure is based mainly on 2D NMR ... [more ▼]

A new indolinic cryptoalkaloid, mattogrossine, has een isolated from the roots and branches of Strychnos mattogrossensis collected near Manaus. Elucidation of its structure is based mainly on 2D NMR studies. Two other indolinic alkaloids were also obtained: strychnobrasiline and 12-hydroxy-11-methoxystrychnobrasiline, and their 13C NMR data are provided [less ▲]

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See detailVenecurine, an Indole Alkaloid from Curare
Quetin-Leclercq, Joëlle; Warin, Roger; Bisset, Norman et al

in Phytochemistry (1989), 28(9), 2221-2223

A new quaternary indole alkaloid, venecurine, has been isolated by chromatographic techniques from a curare obtained from the Hoti tribe of Venezuela. Elucidation of its structure is based mainly on 2D ... [more ▼]

A new quaternary indole alkaloid, venecurine, has been isolated by chromatographic techniques from a curare obtained from the Hoti tribe of Venezuela. Elucidation of its structure is based mainly on 2D-NMR studies. Concurrently with the structural work, frog bioassays were carried out. The curare and venecurine exhibit the same type of activity that is relatively low as compared with the dimeric curarizing alkaloids.These results may be an indication that the sample of curare investigated was a weak one intended to be used for capturing rather than killing animals. [less ▲]

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