Chapter 5 Alkaloids of the Calabar Bean

Structure, Bioactivity and Synthesis of Natural Products with Hexahydropyrrolo[2,3‐b]indole

“…The literature contains a few reviews, although these appear to cover only specific aspects of these compounds. These include works by Schmidt and Movassaghi, [97] on biosynthetic hypotheses; Steven and Overman, [98] on syntheses of poly-HPI compounds; and Crich and Banerjee, [99] on the stereochemistry of HPI containing-compounds, as well as classical publications on the Calabar bean alkaloids, [100,101] phenserine, [102] chimonanthine and related natural products, [103,104] chaetocin and related natural products, [105] and the chemistry of cyclic tautomers of tryptamines and Trp. [106,107] This article provides an exhaustive overview of the structure, synthesis and bioactivity of HPI and HPIC containing natural products from all of the aforementioned structural classes, emphasizing the synthetic routes to polycyclic compounds of this type published until December 2009.…”

Phosphonium Salts as Chiral Phase‐Transfer Catalysts: Asymmetric Michael and Mannich Reactions of 3‐Aryloxindoles

“…Furthermore, a three-step transformation of 3 r was realized to afford, after only a single purification step, compounds 6 and 7, which have a core structure similar to important natural products such as CPC-1, (À)-physostigmine, (À)-pseudophrynaminol, etc. [9,10] These natural product analogues might possess important biological activity and are therefore valuable for the drug discovery.…”

Efficient Alkynylation of 2‐Oxindoles with Alkynyl Dibenzothiophenium Triflates: Total Synthesis of (±)‐Deoxyeseroline

“…In this regard, construction of compounds having all‐carbon quaternary centers is a long lasting challenge to address owing to the resultant steric congestion . In case of complex pyrroloindoline as well as many other naturally occurring Calabar alkaloids, 2‐oxindoles having all‐carbon quaternary centers at the benzylic position, are found to be essential intermediates in their total syntheses ( 1 a – f , Figure ) –…”