<p>The major part of this thesis describes the synthesis of enantiopure alcohols and diols by combining ruthenium-catalyzed racemization or epimerization and lipase-catalyzed asymmetric transformations. A minor part of this thesis is focused on ruthenium-catalyzed redox reactions for transfer hydrogenation of 1,3-cycloalkanediketones. </p><p>Kinetic resolution of racemic γ-hydroxy acid derivatives was performed via <i>Pseudomonas cepacia</i> lipase (PS-C)-catalyzed transesterification. γ-Hydroxy esters and γ-hydroxy amides were studied showing in higher selec-tivity and yields for the γ-hydroxy amides. The enzyme PS-C tolerates both variation in the chain length and different functionalities giving good to high enantioselectivity. Combining enzymatic kinetic resolution with a ruthenium-catalyzed racemization led to a dynamic kinetic resolution (DKR). The use of 2,4-dimethyl-3-pentanol as a hydrogen source to suppress ketone formation in the dynamic kinetic resolution increased the yields of the acetate product. The synthetic utility of this procedure was illustrated by the practical synthesis of the γ-lactone (R)-5-methyltetrahydrofuran-2-one.</p><p>A distereoselective transformation of <i>cis/trans</i>-1,3-cyclohexandiol using <i>Candida antarctica</i> lipase B (CALB)-catalyzed transesterification was of interest. Desymmetrization of <i>cis</i>-1,3-cyclohexanediol to the (<i>R</i>-monoacetate was successfully accomplished. Enantiopure (<i>R,R</i>)-diacetate was obtained from the (<i>R</i>)-monoacetate in a DYKAT process at room tem-perature. Metal- and enzyme-catalyzed transformation of <i>cis/trans</i>-1,3-cyclohexanediol using PS-C, gives a high diastereoselectivity for cis-diacetate. The (<i>S</i>)-mono-acetate was obtained from <i>cis</i>-diacetate by CALB-catalyzed hydrolysis. In addition, it was shown, by the use of deuterium-labeling that intramolecular acyl migration does not occur in the transformation of <i>cis</i>-monoacetate to the <i>cis</i>-diacetate. </p><p>Ruthenium-catalyzed transfer hydrogenation of 1,3-cyclohexanedione under microwave heating was developed as an efficient and fast method for the preparation of 1,3-cycloalkandiols.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:su-789 |
| Date | January 2006 |
| Creators | Fransson, Ann-Britt L. |
| Publisher | Stockholm University, Department of Organic Chemistry, Stockholm : Institutionen för organisk kemi |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
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