- Convenient Enzymatic Resolution of Alcohols Using Highly Reactive, Nonharmful Acyl Donors, 1-Ethoxyvinyl Esters
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1-Ethoxyvinyl esters 3, a new type of acyl donors for enzymatic resolution of racemic alcohols, were disclosed to be superior to the contemporary major reagents, vinyl esters 1 and isopropenyl esters 2. Three features of 3 are noticeable: (1) 3 generates ethyl acetate as a single coproduct, which does not affect any enzymes, while acetaldehyde liberated from 1 deactivates some kinds of lipases. (2) The reactivity of 3 was not less than that of 1 and much higher than that of 2, and the optical purity of the products was as high as that of 1 and 2. Especially, it was generally observed that 3 showed higher reactivity than 1 for reactions using Candida rugosa lipases, one of the most commonly employed lipases, having liberal applicability to substrates but sensitive to acetaldehyde. Twelve examples of the kinetic resolution of racemic secondary alcohols (5 and 10) and one desymmetrization of meso-alcohol 7 were presented employing the acetate 3a or the octanoate 3b and four types of lipases. (3) A one-pot procedure for the preparation of 3 from the corresponding carboxylic acid and the subsequent enzymatic resolution of alcohols, which has not been reported using 1 or 2, was elucidated. The chemical and optical yields of the products by this procedure were similar to those obtained using isolated 3.
- Kita, Yasuyuki,Takebe, Yasushi,Murata, Kenji,Naka, Tadaatsu,Akai, Shuji
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- Enantiomers of cis- and trans-3-(4-propyl-cyclopent-2-enyl) propyl acetate. A study on the bioactive conformation and chiral recognition of a moth sex pheromone component
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The enantiomers of cis- and trans-3-(4-propyl-cyclopent-2-enyl) propyl acetate, which are conformationally constrained analogues of (Z)-5-decenyl acetate (1), a sex pheromone component of the turnip moth, Agrotis segetum, have been synthesized and tested using the elcctrophysiological single-sensillum technique. The analogues mimic a cisoid and transoid conformation of 1, respectively. In addition, the enantiomers of each of the cis- and trans-isomers are conformationally constrained analogues of enantiomeric cisoid and transoid conformations of 1. Thus, the compounds prepared and tested are well suited to investigate the nature of the bioactive conformation of the natural pheromone component 1 and the chiral sense of its interaction with the receptor. Electrophysiological single-sensillum recordings show that the activity of the most active cis-isomer, which has a (1S,4R)-configuration, is more than two orders of magnitude higher than that of the most active trans-isomer. Furthermore, the (1S,4R)-isomer is at least 100 times more active than its enantiomer. These results strongly support a previously proposed cisoid bioactive conformation of 1. Furthermore, the (1S,4R)-configuration of most active stereoisomer identifies the chiral sense of the interaction between the natural pheromone component 1 and its receptor.
- Gustavsson, Anna-Lena,Larsson, Mattias C.,Hansson, Bill S.,Liljefors, Tommy
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p. 2173 - 2183
(2007/10/03)
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- Stereoselectivity of 2-methyl-2-norpinyl cations
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Optically active (1S)-1-methylbicyclo[2.2.1]heptan-2-one (25) was prepared by starting from (1R)-bicyclo[2.2.1]heptan-2-one (21). Photolysis of the tosylhydrazone 8 of 25 generates, in part, 1-methylbicyclo[2.2.1]heptane-endo-2-diazonium ions (10) from which 1-methylbicyclo[2.2.1]heptan-endo-2-ol (14) and 2-methylbicyclo[3.1.1]heptan-2-ol (16) arise. The ee of both products (42-45%) was found to agree within experimental error. These data point to the bridged 2-methyl-2-norpinyl cation (13) as the most stable structure. Racemization of 13 via the open 2-methyl-2-norpinyl cation (17) as the transition state competes with nucleophilic capture. VCH Verlagsgesellschaft mbH, 1996.
- Herrmann, Roland,Kirmse, Wolfgang
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p. 435 - 438
(2007/10/03)
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