Cyclopropenones in the synthesis of indolizidine, pyrrolo[2, 1-a]isoquinoline and indolizino[8, 7-b]indole alkaloids. Issue 45 (6th November 2020)

• Record Type: Journal Article
• Authors: Jamshaid, Faisal; Kondakal, Vishnu V.R.; Newman, C. Declan; Dobson, Rhianne; João, Heidi; Rice, Craig R.; Mwansa, Joseph M.; Thapa, Bimod; Hemming, Karl
• Is Part Of: Tetrahedron. Volume 76:Issue 45(2020)
• Publication Date: 2020-11-06
• Subjects: Indolizidine -- Pyrroloisoquinoline -- Indolizinoindole -- Castanospermine -- Cyclopropenone -- Oxidation; Chemistry, Organic -- Periodicals; 547.005
• DOI: 10.1016/j.tet.2020.131570
• Languages: English
• ISSNs: 0040-4020

Abstract

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. Graphical abstract: Image 1