Enzymatic oxidation of aromatic substrates via toluene dioxygenase and catechol dehydrogenase. Application to total synthesis of combretastatins A-1 and B-1

Toluene dioxygenase (TDO)-carrying microorganisms, the Pseudomonas putida F39/D and the genetically engineered Escherichia coli JM109 (pDTG601), were used to investigate the enzyme's kinetic resolution power in resolving aromatic substrate with remote chiral center. In the biotransformation of 1-phenyl-ethanol with P. putida F39/D, the S-enantiomer was consumed at faster rate than its R-counter part. However, when the same substrate was oxidized using E. coli JM109 (pDTG601), both enantiomers were oxidized indiscriminately at the same rate. Similar substrates with larger substituents at the stereogenic center were also oxidized without any preference for either enantiomer by JM109 (pDTG601). Biotransformation of cyclopropylbenzene was carried out to investigate whether or not the biotransformation process goes through a radical intermediate. New metabolites obtain in these studies were isolated, characterized, and their absolute stereochemistry were established through conventional chemical manipulations.; A series of substituted catechols were made using E. coli JM109 (pDTG602), which carries the toluene cis-dihydrodiol dehydrogenase (TDDH), as the source of biocatalyst. 4-Bromoanisole catechol obtained through biotransformation of corresponding arene, 4-bromoanisole, with JM109 (pDTG602) was used in the total syntheses of Combretastatins A-1 and B-1. (1S, 2S)-3-bromocyclohexa-3,5-diene-1,2-diol was also used as chiral synthon for synthesis of polyhydroxylated chiral polymer.