Chemoenzymatic synthesis of conduritol analogues

Diastereocontrolled Construction of Spiroindolenines via Hexafluoroisopropanol-Promoted Dearomative Epoxide-Indole Cyclization

Herein, we report the discovery of the ipso-selective, dearomatizing spirocyclization of indole-tethered epoxides as a fundamentally new approach for constructing spiroindolenines equipped with three contiguous stereogenic centers under complete diastereocontrol (dr >99:1) and in high yields. Promoted by hexafluoroisopropanol, the protocol features a broad substrate scope, easy scale-up, and versatile transformations of the synthesized spiroindolenines.

An engineered toluene dioxygenase for a single step biocatalytical production of (-)-(1S,2R)-cis-1,2-dihydro-1,2-naphthalenediol

cis-1,2-Dihydro-1,2-naphthalenediol (DHND) is a valuable molecule employed for the pharmaceutical synthesis of bioactive compounds, such as bicyclic conduritol analogues. Enantiopure (+)-(1R,2S)-DHND (>98 % ee) is easily biosynthesized through the dearomatizing dihydroxylation of naphthalene, catalyzed by toluene dioxygenase (TDO) from Pseudomonas putida F1. However, the opposite enantiomer (-)-(1S,2R)-DHND could not be directly accessed, neither by chemical synthesis nor via biocatalytic approaches. Herein, we report a one-step biosynthesis of the opposite enantiomer (-)-(1S,2R)-DHND in a recombinant TDO E. coli BW25113 platform. We based on a semi-rational approach to generate a set of TDO variants, targeting exclusively the hotspot position F366, in order to enable an enantiomeric switch in the generated product. Eight out of nine single point variants were active and showed not only an alteration in enantioselectivity, but also generated an enantiomeric excess of the pursued product. Variant TDO_F366V outperformed above the rest of the set, enabling the synthesis of (-)-(1S,2R)-DHND not only with an excellent enantiomeric excess of 90 %, but also with an advantageous product formation. A comparative semi-preparative biosynthesis yielded, 287 mg of (+)-(1R,2S)-DHND (>98 % ee) and 101 mg of (-)-(1S,2R)-DHND (90 % ee), when performed in a total volume of 100 mL with TDO wild-type and TDO_F366V resting cells, respectively.

A diversity-oriented synthesis of bicyclic cis-dihydroarenediols, cis-4-hydroxyscytalones, and bicyclic conduritol analogues

A common-intermediate-based enantioselective strategy has been developed aiming at bicyclic arene cis-dihydrodiols, cis-4-hydroxyscytalones, and bicyclic mimics of conduritol. Key features of this protocol include Barrett's asymmetric hydroxyallylation, ring-closing metathesis (RCM), and completely regioselective Wacker oxidation of internal cyclic olefins.

Regio- and stereospecific synthesis of a new benzoconduritol-C derivative

A stereospecific synthesis of 3-(2-bromophenoxy)-1,2,3,4-tetrahydronaphthalen-1,2,4-triol (benzoconduritol-C derivative) has been achieved by a fully regio- and stereospecific rhodium catalysed reaction of oxabenzonorbornadiene in the presence of 2-bromophenol.