Analogues of amphibian alkaloids: total synthesis of (5R,8S,8aS)-(−)-8-methyl- 5-pentyloctahydroindolizine (8-epi-indolizidine 209B) and [(1S,4R,9aS)-(−)-4-pentyloctahydro- 2H-quinolizin- 1-yl]methanol

• Joseph P. Michael,
• Claudia Accone,
• Charles B. de Koning and
• Christiaan W. van der Westhuyzen

Beilstein J. Org. Chem. 2008, 4, No. 5, doi:10.1186/1860-5397-4-5

• Raney nickel [25] in boiling ethanol to give (−)-(5R,8S,8aS)-8-methyl-5-pentyloctahydroindolizine (8-epi-indolizidine 209B) 9 in 74% yield. The spectroscopic data for this product agreed with those reported for the racemate. Support for the cis-relationship of the hydrogen atoms at C-5 and C-8a in all

• cis-hydrogenation of 39. While it would have been desirable to conclude this investigation by preparing (1S,4R,9aS)-4-pentyloctahydro-2H-quinolizine 42, the ring homologue of 8-epi-indolizidine 209B, this target eluded us. Attempts to reduce the corresponding methanesulfonate of 41 with Raney nickel

A convenient allylsilane- N-acyliminium route toward indolizidine and quinolizidine alkaloids

• Roland Remuson

Beilstein J. Org. Chem. 2007, 3, No. 32, doi:10.1186/1860-5397-3-32

• were the conversion of 7b into its dithiolane and subsequent desulfurisation using Raney nickel. The synthesis of (-)-indolizidine 167B 1 has been achieved in 7 steps with a 17% overall yield from ethyl (3R)-3-aminohexanoate 2 with an enantiomeric excess of 93%. [19] I 1.2 Intermolecular cyclisation