Indolizidine and quinolizidine alkaloids

Asymmetric synthesis of the optically active piperidine alkaloid (+)-β-conhydrine

“…The mixture was stirred at rt for 12 h, filtered and after evaporation of the solvent, the crude product was purified by flash column chromatography on silica gel using AcOEt-PE (20:80) as eluent to afford the hydrazone (2R,2S)-12 (4.48 g, 86%) as a colorless oil. 2,26.6,27.5,49.6,59.3,63.0,70.2,74.6,80.8,127.3,127.9,128.3,136.6,139.0. Anal.…”

“…13 C NMR (CDCl 3 , 75 MHz): d 9. 2,21.5,25.4,26.7,36.2,51.8,58.9,59.0,60.2,73.7,74.1,79.2,117.0,126.3,127.3,128.0,128.1,136.1,136.3,137.2,169.6. Anal.…”

“…The filtrate was concentrated under vacuum and purification of the residue by column chromatography on silica gel using AcOEt-PE (80:20) as eluent gave piperidin-2-ones 9 (218 mg, 90%), 10 (256 mg, 95%) and 17 (144 mg, 92%) as a yellow oil. 2,23.4,27.1,27.3,33.7,53.5,58.8,60.3,64.1,67.3,75.1,168.9. Anal.…”

“…piperidines fall into this category and consequently have attracted considerable attention from the synthetic community because of their potent antiviral and antitumor activities. 1,2 This class of compounds includes a-and b-conhydrine; their stereoisomers ( Fig. 1) are representatives of the hemlock alkaloids isolated from the seeds and leaves of the poisonous plant Conium maculatum L., whose extracts were used in Ancient Greece to get rid of criminals and undesirable intellectuals, for example, Socrates.…”

Synthesis of pyrrolizidine alkaloids via 1,3-dipolar cycloaddition involving cyclic nitrones and unsaturated lactones

“…3 For these reasons, the synthesis of the iminosugars and their analogues has attracted attention of many academic and pharmaceutical laboratories including our group. [3][4][5][6] Recently, we have reported that the 1,3-dipolar cycloaddition of five-membered cyclic nitrones to the a,b-unsaturated d-lactones provides an attractive entry to the pyrrolizidine and indolizidine iminosugars. 6 We found that the cycloadditions involving d-lactones proceed exclusively in the exo mode, and therefore in many cases only a single product is formed.…”