Arene Alkylation Biocatalytic Friedel-Crafts

Squalene-hopene cyclase (SHC) enzymes have been used to effect intramolecular biocatalytic Friedel-Crafts reactions of phenyl ethers [27]. The natural substrate for such enzymes, squalene, is a C hexaene, but it has been demonstrated that an SHC from Zymomonas mobilis can accept a 

SCHEME 32,5 Tandem cycUzation/aryl alkylation catalyzed by squalene hopene cyclase. 

In some cases, such prenyltransferase enzymes can process substituted tryptophans 53 and/or different alkylating agents other than DMAPP, the common requirement being that the alkylating agent 54 is able to form a stabilized (allylic/benzylic) carbocation, although the regioselectivity in 

SCHEME 32.7 Substitution of L-tryptophan derivatives 53 with other alkyl groups. 

SCHEME 32.8 Eormation of enantiopiire tetracycle 57 from racemic 56. 

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