Alkaloids of the ant Chelaner antarcticus

Radical Couplings as Key Steps for the Preparation of Derivatives of Nonactic Acid

“…Reaction of 2-furyllithium with propylene oxide at 0 C is described in the literature to give 1-(furan-2-yl)propan-2-ol (6b) in good yield in THF [9] as solvent. However, we obtained low yields under these reported conditions but the reaction in diethyl ether [10] at 10 C gave 6b in 86% yield (Table 1). Both radical and anionic couplings are regioselective in the 2-position of furan (3).…”

Two-directional synthesis and biological evaluation of alkaloid 5-epi-cis-275B′

“…Our optimised conditions for the triple reductive cyclisation was then successfully applied to 25 triketone 9, which, upon reaction gave (±)-xenovenine 2 as a single diasteroisomer in 24% yield. Jones reported a related triple reductive amination in his report of the isolation of xenovenine, 11 which gave a mixture of diastereomers. We were therefore particularly pleased to find that our optimised procedure gave the 30 product as a single diastereomer.…”

“…35 The main toxic activity of plant PAs appears to be hepatotoxicity, caused indirectly by pyrrole metabolites. 11 Other alkaloids isolated from anurans are known to display neurotoxic activity by interacting directly with specific ion channels within the nervous system. One recognised target is the nicotinic acetylcholine 40 receptor.…”

Cis-trans-conversion of the bicycle in pyrrolizidines: The effect of the preferred conformations on the properties of the bases and the thermodynamics of conformational transformation of the ring fusion type. (Review)

“…Its proportion in the mixture was comparatively small [20]. In [21] a mixture of the isomeric bases 39-42 was obtained by a series of transformations differing little from those described in [20].…”

“…However, there are strong angular strains in forms A [2,14,15,17]. In spite of this many pyrrolizidine derivatives of types 6 and 7 exist preferentially in the trans-fused conformations A [14,[17][18][19][20][21][22][23], demonstrating the considerable supremacy of the cis-fused forms B with respect to strain that determines the preference for the A forms.…”