Biochemical reductions hydroxy ketones

Reduction of diketones to either hydroxy ketones or diols can be accomplished by different biochemical reductions [327, 834] Procedure 50, p. 218). 

This article will focus on new developments on the field of NAD(P)-depen-dent dehydrogenases, in particular on new alcohol dehydrogenases applicable for preparative chemistry. Biochemical properties of dehydrogenases useful for the synthesis of chiral hydroxy esters and alcohols are summarized in this contribution with respect to more recent studies on enantioselective reduction of prochiral ketones and to new enzymes for this purpose. Reviews covering earlier works in this field can be found in [42-44],... 

Figure 20-5. Biochemical pathway for ketogene-sis. Condensation of three molecules of acetyl-CoA results in synthesis of 3-hydroxy-3-methyl-glutaryl (HMG)-CoA and release of free CoA-SH, which is then available for continued P-oxidation. Deficiency of HMG-CoA lyase results in the inability to cleave the HMG-CoA to form acetoacetate (the initial ketone body ) and its reduction product P-hydroxybutyrate.

Hemiacetals are formed from hydroxy aldehydes " or ketones which are usually first in a protected form and are deblocked prior to cyclization. Ozonolysis of cyclohexene derivative 5 and reductive workup, followed by hydrolysis of the acid chloride formed in situ and borane reduction of the carboxylic acid, leads to the six-membered hemiacetal 6. a precursor for fluo-rinated sugars that are potentially versatile as molecular probes in the elucidation of biochemical processes. ... 

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