22 research outputs found
Photos convey magic of '60s jazz scene
Photocopied article form the newspaper Star Tonight about Basil Breakey and how he met other contemporary jazz musicians such as Chris McGregor and Abdullah Ibrahim
‘Every day a new shop pops up’ – South Africa's ‘New’ Chinese Diaspora and the Multilingual Transformation of Rural Towns
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
Background<p>Prior work from these laboratories has centred on the development of enaminones as versatile intermediates for the synthesis of alkaloids and other nitrogen-containing heterocycles. In this paper we describe the enantioselective synthesis of indolizidine and quinolizidine analogues of bicyclic amphibian alkaloids via pyrrolidinylidene- and piperidinylidene-containing enaminones.</p><p>Results</p><p>Our previously reported synthesis of racemic 8-epi-indolizidine 209B has been extended to the laevorotatory enantiomer, (−)-9. Attempts to adapt the synthetic route in order to obtain quinolizidine analogues revealed that a key piperidinylidene-containing enaminone intermediate (+)-28 was less tractable than its pyrrolidinylidene counterpart, thereby necessitating modifications that included timing changes and additional protection–deprotection steps. A successful synthesis of [(1S,4R,9aS)-4-pentyloctahydro-2H-quinolizin-1-yl]methanol (−)-41 from the chiral amine tert-butyl (3R)-3-{benzyl[(1R)-1-phenylethyl]amino}octanoate (+)-14 was achieved in 14 steps and an overall yield of 20.4%.</p><p>Conclusion</p><p>The methodology reported in this article was successfully applied to the enantioselective synthesis of the title compounds. It paves the way for the total synthesis of a range of cis-5,8-disubstituted indolizidines and cis-1,4-disubstituted quinolizidines, as well as the naturally occurring trans-disubstituted alkaloids.</p