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New non‐ionic hydrogels were synthesized by radical homopolymerization of vinyl end‐functionalized poly(2‐methyl‐2‐oxazoline) bis(macromonomers), or by radical copolymerization of these bis(macromonomers) with N‐vinyl‐2‐pyrrolidone (NVP). The poly(2‐methyl‐2‐oxazoline) bis(macromonomers) were synthesized through “living” cationic ring‐opening polymerization of 2‐methyl‐2‐oxazoline (MeOXA), using, simultaneously, the known “initiating” and “end‐capping” method for synthesis of macromonomers. Chloromethyl styrene was used as initiator and N‐(4‐vinylbenzyl)‐piperazine was used as the terminating agent. Well defined poly(2‐methyl‐2‐oxazoline) bis(macromonomers) were obtained with Pn = 4, 11, and 17. The hydrogel structures were characterized by high‐resolution magic angle spinning NMR technique and their solvent absorption capacity was tested by swelling experiments in different solvents. The bis(macromonomers) were characterized by NMR spectroscopy and gel permeation chromatography.Schematic of polymerizationmagnified imageSchematic of polymerization

Abstract:The antiproliferative activity of a set of seven natural Amaryllidaceae alkaloids and 32 derivatives against four cancer cell lines (A2780, SW1573, T47-D and WiDr) was determined. The best antiproliferative activities were achieved with alkaloids derived from pancracine (2), haemanthamine (6) and haemantidine (7). For each skeleton, some structure-activity relationships were outlined.

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An unexpected rearrangement of haemanthamine-type alkaloids in the presence of halogenating agents has been found. Rearranged compounds present the 5,11-methanomorphantridine framework characteristic of montanine-type alkaloids. These compounds are difficult to obtain because of their scarcity in natural sources and because the synthetic approaches developed so far require numerous steps. Vibrational circular dichroism (VCD) spectroscopy was used to determine the absolute configuration of one of the rearranged compounds. Several rearranged alkaloids showed antimalarial activity.

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Four new alkaloids (1-4) have been isolated from a methanolic extract of bulbs of Pancratium canariense, together with 12 known alkaloids (5-16). The structures of the new alkaloids were determined by extensive 1D and 2D NMR spectroscopic studies and X-ray diffraction.

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