Divergent ketone reduction

Divergent RRM Using a Single Chiral Reagent Ketone Reduction... 

The iyn-preference of 105b and 105c is similar to those observed in the reduction of the related ketones, 34 and in the epoxidation and dihydroxylation of the related olefins 71 [104]. Although the trajectories of the attacking reagents are considered to be different in these reactions [83-87, 170, 171], all three types of reactions favor iyn-addition, which excludes a predominant role of divergent trajectories in these dibenzobicyclic systems. 

One last case of enzymatic divergent RRM is described in Scheme 6.6 from the work of Dehh and Go tor (Scheme 6.6) [16]. The fungus Moiiierella isabellim was used for the reduction of the cyano ketone mc-29. Two separable alcohol... 

A separation in the metabolic route occurs on the reduction of the double bond of A -androstene-3,17-dione (LV), affording two saturated diketones isomeric at Cs. These are rings A/B trans, androstane-3,17-dione (LX), and rings A/B cis, etiocholane-3,17-dione (LXI). Both of these diketones have been isolated from urine. " That these two diketones are true metabolites of testosterone has been shown by the isolation of the tagged substances after injection of deuterium-labeled hormone. Once the metabolic course has diverged upon the reduction of the a, unsaturated ketone to the isomeric diketones, there is no crossing over from one branch of the pathway to the other. Thus, after the administration of either deuterium-labeled or nonisotopic androstane-3,17-dione (LX), only... 

In some transformations, the choice of solvent represents a powerful adjuster bolt for the stereochemical outcome of the reaction. Divergent stereoselectivity in the reduction of glycid ketones 131 is observed when either diethyl ether or HMPA was used with trimethoxy silane as reducing reagent in the presence of catalytic amounts of lithium methoxide (Table 3.2) [49]. Highly coordinated silicon compounds show specific reactivities in comparison to tetra-coordinated silicon compounds [50]. 

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