Total syntheses of (±)-folicanthine and (±)-chimonanthine via a double intramolecular carbamoylketene–alkene [2+2] cycloaddition

Simple indole alkaloids and those with a nonrearranged monoterpenoid unit

“…A common intermediate 1005 was prepared from bis-carboxylic acid involving [2 + 2] cycloaddition of dienyl ketene and selective ring-expansion of bis-cyclobutanone sequences (Scheme 196). 316 The nickel-catalyzed homocoupling reaction of tertiary alkyl bromide 1006 derived from tryptamine was successfully applied for the construction of bispyrrolo [2,3-b]indoline 1007…”

Recent Advances of Transition Metal‐Mediated Oxidative Radical Reactions in Total Synthesis of Indole Alkaloids

“…Many similar protocols were also developed for the construction of vicinal all-carbon quaternary centers from the oxindole intermediate. Methods that provided the target molecules by intramolecular carbamoylketenealkene [2＋2] cycloaddition, [26] nucleophilic dimerization of 1-hydroxymelatonin, [27] photolysis of 3a-phenylselenylpyrroloindoline, [28] and the oxidative coupling of submitted tryptamine/tryptophan derivatives have also been reported. A similar transversion can also be mediated by Zn/Ni or Mn/Ni.…”

Stereocontrolled Total Synthesis of Natural Products with Characteristic Molecular Structures and Biological Activities

“…To date, we have successfully achieved formal syntheses of physovenine (144) 77) and physostigmine (145), 78) and total syntheses of debromoflustramines B (146), E (147), 79) folicanthine (148) and chimonanthine (149) 80) based on the cycloaddition methodology, as shown in Chart 28.…”

“…[77][78][79][80] The chemical yield obtained in the cycloaddition is uniformly high, and the subsequent transformations proceed smoothly and selectively to give the alkaloids or the key intermediates as racemic forms. We thought it important to make the reaction asymmetric.…”