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Synthetic Studies Toward the Flatworm‐Derived Alkaloid Pseudocerosine
Author(s) -
Kim Se Hun,
Sperry Jonathan
Publication year - 2019
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201903659
Subject(s) - tryptamine , chemistry , aminal , moiety , enamine , total synthesis , iminium , flatworm , stereochemistry , pterin , tryptamines , combinatorial chemistry , organic chemistry , biology , zoology , biochemistry , cofactor , catalysis , enzyme
Pseudocerosine, the pigment responsible for the vivid blue spots along the tunic rim of the marine flatworm Pseudoceros indicus, possesses a molecular framework that is unique among heteroaromatic natural products. Herein we provide an overview of several synthetic approaches to the alkaloid pseudocerosine, focusing in particular on the azafulvene‐embedded azepinoindole and the aminal moiety. Two distinct approaches to the azepinoindole core were successful. The first involved C−H borylation of a tryptamine derivative followed by Suzuki‐Miyaura coupling with an α‐bromoenone and base mediated cyclisation. The second involved the selective formation of a conjugated enamine from a tryptamine and an enone, followed by an acid‐mediated Mannich‐type enamine cyclisation. It has also been demonstrated that the unusual aminal present in pseudocerosine can be installed by the reaction of acetamide with a pyridoindole‐based iminium ion. These studies provide valuable insight into the reactivity and stability of the pseudocerosine core structure and serve as a platform for its total synthesis.