AmaryllidaceaeAlkaloids: (+)-Tazettine, (+)-3-O-Demethylcriwelline and (+)-3-Epimacronine at 173 K

In vitro Antiplasmodial Activities of Alkaloids Isolated from Roots of Worsleya procera (Lem.) Traub (Amaryllidaceae)

“…Regarding the molecular conformation, an S-configuration was observed in each chiral center during the refinement. In this way, the structure reported herein matches very well with the one reported by Linden et al, 48 with a very low root mean square deviation value (RMS 0.00681). As discussed by Linden et al, 48 all the structural parameters are in a normal range of expected values.…”

“…However, structure was reported with error on absolute-configuration in 1996 47 because no accurate experiment was carried out. Then in 1998, 48 a more rigorous experiment at low temperature was reported, giving, therefore, a more accurate structure. In this work, the structural determination was conducted at 178 K, facilitating the scattering and allowing a more reliable absolute structure determination.…”

“…In this work, the structural determination was conducted at 178 K, facilitating the scattering and allowing a more reliable absolute structure determination. Indeed, Linden et al 48 refined their structure based on the comparison with the derivative N-methyltazettine iodide, 49 once no meaningful anomalous scattering was observed for tazettine compound using Mo radiation.…”

Three New Tazettine-Type Alkaloids from Galanthus gracilis and Galanthus plicatus Subsp. byzantinus

“…Moreover, a thorough evaluation of the coupling constants shared by the ring C hydrogens, using Dreiding models, provides further proof to the a-orientation of the hydroxy group at C-3. The aforementioned results also point to the half chair conformation of ring C. Supporting evidence for the conformational and configurational preferences of 1 is provided by an X-ray crystallographic analysis (16).…”

“…A CD-curve of 2, strikingly similar to that of (1)-3-epimacronine (6) of established stereochemistry (11,16), indicates that the former adopts the same C-12b S-chirality. The C-6a Rconfiguration of 2, as deduced from the vicinal coupling constants observed for the three-spin system formed by H-6a, H-6b and H-6a (17), is also shared by compounds 5 and 6.…”