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Regioselective Enzymatic Halogenation of Substituted Tryptophan Derivatives using the FAD‐Dependent Halogenase RebH
Author(s) -
Frese Marcel,
Guzowska Paulina H.,
Voß Hauke,
Sewald Norbert
Publication year - 2014
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201301090
Subject(s) - regioselectivity , halogenation , chemistry , electrophile , organic chemistry , halide , tryptophan , halogen , combinatorial chemistry , catalysis , alkyl , amino acid , biochemistry
Regioselective methods to establish carbon–halide bonds are still rare, although halogenation is considered as a commonly used methodology for the functionalization of organic compounds. The incorporation of halogen substituents by organic synthesis usually requires hazardous conditions, shows poor regioselectivity and results in the formation of unwanted byproducts. In addition, halogenation by electrophilic aromatic substitution (S E Ar) obeys distinct rules depending on electron‐withdrawing or ‐donating groups already present in the aromatic ring. We employed the tryptophan‐7‐halogenase RebH for regioselective enzymatic halogenation to overcome these limitations. In combination with a tryptophan synthase, an array of C5‐ and C6‐substituted tryptophan derivatives was synthesized and halogenated by RebH. The halogenase is able override these directing effects and halogenates at the electronically unfavored C7‐ meta ‐position, even in presence of ortho / para ‐directing groups.