Enzymatic cyclizations using laccases: Multiple bond formation between dihydroxybenzoic acid derivatives and aromatic amines

Abstract

Oxidative C–N bond formation followed by cyclization of dihydroxybenzoic acid derivatives with aromatic and heteroaromatic amines was catalyzed in the presence of oxygen by laccases [E.C. 1.10.3.2] from the white rot fungi Pycnoporus cinnabarinus and Myceliophthora thermophila. The laccase-catalyzed formation of cycloheptenes, cyclooctenes, diazaspiro cyclohexenes, and phenazines was investigated for the first time with regard to the ring size and substituents of the aromatic amines as well as to the substitution patterns of the substrates. Differences to C–N bond formation without cyclization are discussed.