Reduction of Hydroxy and Amino Ketones

Hydroxy ketones and hydroxy-a,/3-unsaturated ketones in the steroids such as estrone and testosterone, respectively, can be reduced to diols biochemically. Estrone acetate gave 68% yield of a-estradiol on incubation with baker s yeast at room temperature after five days [909]. Testosterone was reduced by bacteria to the saturated hydroxy ketones, etiocholan-17-ol-3-one and androstan-17-ol-3-one, and further to the diols, ep/-etiocholane-3,17-diol and the epimeric isoandrostane-3,17-diol, both in low yields [329]. 

Bacillus polymyxa in a hydrogen atmosphere reduced (R,S)-acetoin to erythro- and /Areo-butane-l,3-diol in 100% yield [910], and Saccharomyces cerevisiae converted 3,3-dimethyl-l-hydroxybutan-2-one to (—)-R-3,3-dimethylbutane-l,2-diol in 66% yield [911]. 

Acyloins were converted to mixtures of stereoisomeric vicinal diols by catalytic hydrogenation over copper chromite [972]. More frequently they were reduced to ketones by zinc (yield 77%) [913, 914], by zinc amalgam (yields 50-60%) [975], by tin (yields 86-92%) [173], or by hydriodic acid by refluxing with 47% hydriodic acid in glacial acetic acid (yields 70-90%) [916], or by treatment with red phosphorus and iodine in carbon disulfide at room temperature (yields 80-90%) [917] Procedure 41, p. 215). Since acyloins are readily accessible by reductive condensation of esters (p. 152) the above reductions provide a very good route to ketones and the best route to macro-cyclic ketones [973]. 

In steroidal a-hydroxy ketones with the keto group in position 20 and the hydroxylic group in position 17, the hydroxy, and better still, acetoxy group is replaced by hydrogen on refluxing for 24 hours with zinc dust and acetic 

Complete redaction of acyloins to hydrocarbons was accomplished by the Clemmensen reduction. Sebacoin afforded cyclodecane in 79% yield [975], and benzoin gave 1,2-diphenylethane in 84% yield [755], 

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