Cyclopropenones in the synthesis of indolizidine, pyrrolo[2,1-a]isoquinoline and indolizino[8,7-b]indole alkaloids

Faisal Jamshaid, Vishnu V.R. Kondakal, C. Declan Newman, Rhianne Dobson, Heidi João, Craig R. Rice, Joseph M. Mwansa, Bimod Thapa, Karl Hemming

Research output: Contribution to journalArticle

Abstract

An attempted synthesis of the indolizidine natural product castanospermine resulted in the successful addition of cyclopropenone to a sugar-derived poly-hydroxylated cyclic imine to give an indolizidinone product, but with the installation of an extra hydroxy group at the castanospermine 8a-bridgehead position. This was also observed in our previous approach to the australine and hyacinthacine pyrrolizidine natural products. The same oxidative phenomenon occurred during the synthesis of pyrrolo[1,2-a]isoquinolines from the reaction of aldimine dihydroisoquinolines with cyclopropenones, whereas ketimine based dihydroisoquinolines gave pyrrolo[1,2-a]isoquinolines without bridgehead oxidation. These results may have some significance for the origins of the bridgehead hydroxy natural products jenamidine B1/B2, clazamycin A/B and legonmycin A/B. The precursor cyclic aldimine for the synthesis of the indolizino[8,7-b]indoles gave dimeric indolizino[8,7-b]indoles, whereas the corresponding cyclic ketimines behaved as expected and gave the indolizino[8,7-b]indole core after reaction with cyclopropenones.

Original languageEnglish
Article number131570
Number of pages10
JournalTetrahedron
Volume76
Issue number45
Early online date6 Sep 2020
DOIs
Publication statusE-pub ahead of print - 6 Sep 2020

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