title: Concise and efficient synthesis of calothrixin B.
abstract: A convergent synthesis of the naturally occurring alkaloid Calothrixin B is presented, which used a regioselective hetero-Diels-Alder reaction between a "push-pull" 2-aza-diene and a N-protected 3-bromo-9H-carbazole-1,4-dione to construct the five-ring skeleton of the molecule. Protection of the indole motif with a benzyl group was unattractive for delivery of sufficient target material because the removal of the protecting group had not been high yielding. We therefore elected to temporarily protect the indole motif with a more labile benzyloxycarbonyl group. Accordingly, the synthesis of calothrixin B proceeded in 17% overall yield over 9 steps from the commercially available 1,2,3,9-tetrahydro-4H-carbazol-4-one.
authors.affiliation: Université de Nantes, Nantes Atlantique Universités, CNRS, Faculté des Sciences et des Techniques, Laboratoire de Synthèse Organique (LSO), UMR CNRS 6513, 2, rue de la Houssinière-BP 92208-44322 Nantes, Cedex 3, France.
authors.forename: Drissa
authors.initials: D
authors.lastname: Sissouma
authors.forename: Lucie
authors.initials: L
authors.lastname: Maingot
authors.forename: Sylvain
authors.initials: S
authors.lastname: Collet
authors.forename: André
authors.initials: A
authors.lastname: Guingant
mesh_terms: D000962:Antimalarials / Q000138:chemical synthesis / Q000737:chemistry; D000970:Antineoplastic Agents / Q000138:chemical synthesis / Q000737:chemistry; D002227:Carbazoles / Q000737:chemistry*; D003500:Cyclization; D026121:Indole Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D010084:Oxidation-Reduction
chemical_list: C513019:1,2,3,9-tetrahydro-4H-carbazol-4-one; D000962:Antimalarials; D000970:Antineoplastic Agents; D002227:Carbazoles; D026121:Indole Alkaloids; C418327:calothrixin B