Anodic oxidation of 3,5-dihalogenotyrosines as a model reaction for the biogenesis of the cavernicolins, metabolites of the verongid sponge Aplysina cavernicola

Abstract

Anodic oxidation of 3,5-dibromo-4-methoxyphenylalanine methyl ester 3, led to cavernicolin [3,3a,7,7a-tetrahydro-3a-hydroxyindole-2,6(1H)-dione] model compounds although equilibration to all four possible stereoisomers 4α, 4β, 5α and 5β was a special characteristic of the model compounds only. This may constitute a new model for the biogenesis of the cavernicolins as an alternative to a spirolactone route from oxidation of amino-protected tyrosines. Chemical oxidation gave poor results.