Oxidative rearrangement of indoles: a new approach to the EFHG-tetracyclic core of diazonamide A.
A new approach to the ring EFHG-tetracyclic core fragment of the marine secondary metabolite diazonamide A is described. The route is based on the oxidative rearrangement of 3-arylindole-2-carboxylates. Thus, a range of 3-arylindole-2-carboxylates (3, 8) underwent rearrangement to the corresponding 3,3-disubstituted oxindoles (4, 9) with migration of the ester group upon treatment with tert-butyl hypochlorite followed by acid. The oxindoles 9 with a 3-[2-(4-methoxybenzyloxy)]phenyl substituent underwent cyclization to the tetracyclic aminals 11 following N-protection, reduction, and treatment with methanesulfonic anhydride. The methodology was applied to the tyrosine-indole derivative 17 to give the EFHG-tetracyclic core of diazonamide A.
Poriel
Cyril
C
Department of Chemistry, University of Exeter, Stocker Road, Exeter EX4 4QD, United Kingdom.
Lachia
Mathilde
M
Wilson
Claire
C
Davies
James R
JR
Moody
Christopher J
CJ
D018360:Crystallography, X-Ray; D003500:Cyclization; D006576:Heterocyclic Compounds, 4 or More Rings / Q000737:chemistry*; D007211:Indoles / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D010080:Oxazoles / Q000737:chemistry*; D010084:Oxidation-Reduction; D013237:Stereoisomerism; D050257:Tubulin Modulators / Q000737:chemistry*
D006576:Heterocyclic Compounds, 4 or More Rings; D007211:Indoles; D010080:Oxazoles; D050257:Tubulin Modulators; C408862:diazonamide A