- Asymmetric Cation-Olefin Monocyclization by Engineered Squalene–Hopene Cyclases
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Squalene–hopene cyclases (SHCs) have great potential for the industrial synthesis of enantiopure cyclic terpenoids. A limitation of SHC catalysis has been the enzymes’ strict (S)-enantioselectivity at the stereocenter formed after the first cyclization step. To gain enantio-complementary access to valuable monocyclic terpenoids, an SHC-wild-type library including 18 novel homologs was set up. A previously not described SHC (AciSHC) was found to synthesize small amounts of monocyclic (R)-γ-dihydroionone from (E/Z)-geranylacetone. Using enzyme and process optimization, the conversion to the desired product was increased to 79 %. Notably, analyzed AciSHC variants could finely differentiate between the geometric geranylacetone isomers: While the (Z)-isomer yielded the desired monocyclic (R)-γ-dihydroionone (>99 % ee), the (E)-isomer was converted to the (S,S)-bicyclic ether (>95 % ee). Applying the knowledge gained from the observed stereodivergent and enantioselective transformations to an additional SHC-substrate pair, access to the complementary (S)-γ-dihydroionone (>99.9 % ee) could be obtained.
- Aeberli, Natalie,Berweger, Raphael,Bornscheuer, Uwe T.,Buller, Rebecca,Dossenbach, Sandro,Eichenberger, Michael,Eichhorn, Eric,Flachsmann, Felix,Hüppi, Sean,Hortencio, Lucas,Patsch, David,Voirol, Francis,Vollenweider, Sabine
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p. 26080 - 26086
(2021/09/20)
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- AN ELECTROCHEMICAL CHLORINATIVE ENE-TYPE REACTION OF ISOPRENOIDS
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The chlorinative ene-type reaction of isoprenoids (12) has been performed by electrolysis in CH2Cl2-H2O-NaCl system.The reaction provides useful allylic chlorides 2 for terpene synthesis in high yields and is affected strikingly by the nature of halide ions and solvents. dl-Theaspirane 21 was prepared from α-dihydroionol via the electrolysis.
- Torii, Sigeru,Uneyama, Kenji,Nakai, Toshiyuki,Yasuda, Tsuneo
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p. 2291 - 2294
(2007/10/02)
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