Hydrogenation is a core technology in chemical synthesis. High rates and selectivities are attainable only by the coordination of structurally well-designed catalysts and suitable reaction conditions. The newly devised [RuCl(2)(phosphane)(2)(1,2-diamine)] complexes are excellent precatalysts for homogeneous hydrogenation of simple ketones which lack any functionality capable of interacting with the metal center. This catalyst system allows for the preferential reduction of a C=O function over a coexisting C=C linkage in a 2-propanol solution containing an alkaline base. The hydrogenation tolerates many substituents including F, Cl, Br, I, CF(3), OCH(3), OCH(2)C(6)H(5), COOCH(CH(3))(2), NO(2), NH(2), and NRCOR as well as various electron-rich and -deficient heterocycles. Furthermore, stereoselectivity is easily controlled by the electronic and steric properties (bulkiness and chirality) of the ligands as well as the reaction conditions. Diastereoselectivities observed in the catalytic hydrogenation of cyclic and acyclic ketones with the standard triphenylphosphane/ethylenediamine combination compare well with the best conventional hydride reductions. The use of appropriate chiral diphosphanes, particularly BINAP compounds, and chiral diamines results in rapid and productive asymmetric hydrogenation of a range of aromatic and heteroaromatic ketones and gives a consistently high enantioselectivity. Certain amino and alkoxy ketones can be used as substrates. Cyclic and acyclic alpha,beta-unsaturated ketones can be converted into chiral allyl alcohols of high enantiomeric purity. Hydrogenation of configurationally labile ketones allows for the dynamic kinetic discrimination of diastereomers, epimers, and enantiomers. This new method shows promise in the practical synthesis of a wide variety of chiral alcohols from achiral and chiral ketone substrates. Its versatility is manifested by the asymmetric synthesis of some biologically significant chiral compounds. The high rate and carbonyl selectivity are based on nonclassical metal-ligand bifunctional catalysis involving an 18-electron amino ruthenium hydride complex and a 16-electron amido ruthenium species.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/1521-3773%2820010105%2940%3A1%3C40%3A%3AAID-ANIE40%3E3.0.CO%3B2-5

Asymmetric Catalysis by Architectural and Functional Molecular Engineering: Practical Chemo‐ and Stereoselective Hydrogenation of Ketones

1,2-Amino Alcohols and Their Heterocyclic Derivatives as Chiral Auxiliaries in Asymmetric Synthesis

Oxidative stress: Free radical production in neural degeneration

Mitochondrial oxidative damage contributes significantly to a range of human disorders, including neurodegenerative diseases, ischaemia-reperfusion injury and ageing-associated dysfunction. To prevent this damage we have delivered a molecule containing the active antioxidant moiety of vitamin E to mitochondria. This was carried out by covalently coupling the antioxidant moiety to a lipophilic triphenylphosphonium cation. This mitochondrially targeted antioxidant, 2-[2-(triphenylphosphonio)ethyl]-3,4-dihydro-2, 5,7,8-tetramethyl-2H-1-benzopyran-6-ol bromide (TPPB), accumulated several-hundred fold within the mitochondrial matrix, driven by the organelle's large membrane potential. When cells were incubated with micromolar concentrations of TPPB, they accumulated millimolar concentrations within their mitochondria. The amount of TPPB taken up by mitochondria was approximately 80-fold greater than endogenous levels of vitamin E. Consequently the targeted derivative of vitamin E protected mitochondrial function from oxidative damage far more effectively than vitamin E itself. The mitochondrially targeted antioxidant TPPB has potential as an antioxidant therapy for disorders involving mitochondrial oxidative damage. It also suggests a new family of mitochondrially targeted antioxidants, redox-active and pharmacologically active molecules designed to prevent damage or manipulate mitochondrial function.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1046/j.1432-1327.1999.00543.x

Selective targeting of an antioxidant to mitochondria

Recent advances in the preparation and synthetic applications of oxiranes

6-Hydroxychroman-2-carboxylic acids (I) have been found to be effective antioxidants in animal fats, vegetable oils, and emulsion systems. Two new
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syntheses of these compounds have been developed. Structure-activity correlations for I with various substitutents at C2, C5, C7, and C8 in various test systems have been obtained. In addition, the homologous chroman acetic acids, which are also antioxidants, and a number of other derived compounds have been synthesized. The most effective antioxidant in this series is the tetramethyl compound I (R2=R5=R7=R8=CH3). This compound has activity which compares well with the better commercial antioxidants.

6-Hydroxychroman-2-carboxylic acids: Novel antioxidants

All eight stereoisomers of α-tocopheryl acetate have been synthesized in a state of high chemical and stereoisomeric purity. Key chiral side-chain intermediates were prepared from (+)-(S)-3-hydroxy-2-methylpropanoic acid. New routes to (2R, 4′ RS, 8′ RS)-α-tocopheryl acetate, a mixture of four diastereoisomers, were also developed. A sensitive gas chromatographic method was developed to determine the diastereoisomeric and enantiomeric purity of α-tocopherol samples as the methyl ethers. It was established for the first time that naturally occurring α-tocopherol is essentially a single enantiomer (2 R, 4′ R, 8′ R), synthetic all-rac-α-tocopherol an equimolar mixture of four racemates, and that natural (E)-(7 R, 11 R)-phytol is diastereoisomerically and enantiomerically homogeneous.

Total Synthesis of All Eight Stereoisomers of α‐Tocopheryl Acetate. Determination of their diastereoisomeric and enantiomeric purity by gas chromatography

Asymmetric reductions of .alpha.,.beta.-acetylenic ketones and acetophenone using lithium aluminum hydride complexed with optically active 1,3-amino alcohols

Les substitutions nucleophiles des chromannes du titre avec le [cyano trimethyl] silane sont etudiees. Le catalyseur, TiCl 4 ou SnCl 4 , a une influence sur la regioselectivite des reactions

Lewis acid mediated nucleophilic substitution reactions of 2-alkoxy-3,4-dihydro-2H-1-benzopyrans: regiochemistry and utility in the synthesis of 3,4-dihydro-2H-1-benzopyran-2-carboxylic acids

Gabriel Saucy

Papers

6-Hydroxychroman-2-carboxylic acids: Novel antioxidants

Total Synthesis of All Eight Stereoisomers of α‐Tocopheryl Acetate. Determination of their diastereoisomeric and enantiomeric purity by gas chromatography

Asymmetric reductions of .alpha.,.beta.-acetylenic ketones and acetophenone using lithium aluminum hydride complexed with optically active 1,3-amino alcohols

Lewis acid mediated nucleophilic substitution reactions of 2-alkoxy-3,4-dihydro-2H-1-benzopyrans: regiochemistry and utility in the synthesis of 3,4-dihydro-2H-1-benzopyran-2-carboxylic acids

A new synthesis of .alpha.-tocopherol