Reductive biotransformations of organic compounds by cells or enzymes of yeast

A novel NADH-dependent carbonyl reductase with an extremely broad substrate range from Candida parapsilosis: Purification and characterization

Magnesium-catalyzed enantioselective aldol between ethyl diazoacetate and aromatic, aliphatic, and alpha,beta-unsaturated aldehydes affords alpha-diazo-beta-hydroxy-esters in high enantioselectivities. Aldol adducts resulting from this asymmetric transformation are versatile intermediates toward the synthesis of several ester containing chiral building blocks.

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Magnesium-Catalyzed Asymmetric Direct Aldol Addition of Ethyl Diazoacetate to Aromatic, Aliphatic, and α,β-Unsaturated Aldehydes

Chromium-based oxidants are probably the most widely used of all oxidizing agents. Over the years they have been continually developed and modified to overcome the typical problems that occur during oxidation and to accept wider ranges of substrates with improved selectivities. They have been accepted readily by synthesis chemists since they are easy to handle and are often ‘off the shelf reagents’. However, they are not without their problems: work-up can be problematical; overoxidation can occur; and, at all times, removal of the product from toxic chromium contaminants is a concern, especially with respect to large scale preparations. In an attempt to circumvent these problems the trend has been to develop the use of catalytic and/or supported reagents. This review is concerned for the most part with the applications and limitations of more recent chromium(VI) oxidants. Several other comprehensive reviews have appeared in this area and should be consulted for more detailed descriptions of older methods, chromium(V) oxidants, mechanism of oxidation and for typical experimental procedures.1–5

Oxidation Adjacent to Oxygen of Alcohols by Chromium Reagents

Recent applications of oxochromiumamine complexes as oxidants in organic synthesis. a review

Ethyl 4-benzyloxy-3-oxobutanoate (1c) is reduced by fermenting baker's yeast with stereochemical control which is dependent on the yeast:substrate ratio and the presence or absence of ethanol. Contrary to earlier reports, ethyl levulinate (3a) can be stereospecifically reduced to (+)-(S)-ethyl 4-hydroxypentanoate (4a)(15% yield, >95% optical purity) as shown by the conversion of (4a) into (–)-(S)-5-methyl-γ-valerolactone (5b). Also, ethyl 4-oxo-4-phenylbutanoate (3b) is stereospecifically reduced to the previously unreported (–)-(S)-5-phenyl-γ-butyrolactone (5c). The stereochemistry of compound (5c) has been established by chemical correlation with (–)-(S)-ethyl 3-hydroxy-3-phenylpropanoate (4c), which in turn was prepared by the baker's yeast reduction of ethyl 3-oxo-3-phenylpropanoate (3e).

Studies on the stereochemical control of fermenting baker's yeast mediated reductions: some 3- and 4-oxo esters

Preparation de l'oxydant et etude de son utilisation lors de l'oxydation d'alcools et de thiols

Tetrabutylammonium chlorochromate, a new mild and selective oxidizing agent

Chiral glycines (1a) and (1b) have been synthesized starting from stereospecifically deuteriated 4-aminobutanoic acids (3a) and (3b). Enzymatic decarboxylation of (2S)-glutamic acid (2a) in 2H2O and (2R,S)-[2,4,4-2H3]glutamic acid (2b)+(2c) in H2O afforded (3a) and (3b), respectively. Chemical transformations of deuteriated pyrrolidinones (4a) and (4b) afforded stereospecifically labelled glycines (1a) and (1b) in good yields.

Convenient synthesis of stereospecifically deuteriated glycines from glutamic acid using a combination of enzymatic and chemical methods

(R)-(–)- and (S)-(+)-2-Aminobutane (1) can be synthesized in good yield and high optical purity from (S)-(+)- and (R)-(–)-2-aminobutanol (2) respectively.

Rosangela Casati

Papers

Studies on the stereochemical control of fermenting baker's yeast mediated reductions: some 3- and 4-oxo esters

Tetrabutylammonium chlorochromate, a new mild and selective oxidizing agent

Convenient synthesis of stereospecifically deuteriated glycines from glutamic acid using a combination of enzymatic and chemical methods

Synthesis of (R)- and (S)-2-aminobutane from (S)- and (R)-2-aminobutanol

Synthesis of 3-methyl-1,3,5-pentanetriol and its mono- and diesters