Selective reductions of ketones in the presence of aldehydes with a superabsorbed alcohol dehydrogenase -a "green" alternative to the Luche-Reduction Günter E. Jeromin*, Eugen Huber _______________________________________________________________ The Luche-reduction is one of the rare methods to reduce keto groups in presence of aldehyde groups to the secondary alcohols, while the aldehyde groups remain unaffected. It is a smooth reduction of the carbonyl groups with sodium borohydride in an alcohol/water mixture in the presence of CeCl 3 . The CeCl 3 reacts with the more active aldehyde group to give the geminate diol which is as known not affected by the sodium borohydride. Reduction only or almost only takes place at the not hydrated keto carbonyl group. But aldehydes, which are not fully transformed to the hydrates are also not fully protected and they are reduced partially too. That is with aromatic aldehydes like benzaldehyde the case. We here present a new "green" method 9 to reduce selectively an aromatic keto group in the presence of an aromatic aldehyde group, with good to very good selectivity. No protection of the aldehyde group is necessary, no lanthanoid salts like CeCl 3 are needed. In a recent paper we described the preparation of an enzymatic all-inclusive catalyst for the enantioselective reductions of keto groups to chiral alcohols in organic media. The organic medium is a mixture of 2-propanol with water usually 9:1. The 2-propanol is not only a solvent but essential for the reduction because it regenerates the cofactor NADP to NADPH. We immobilized a total enzyme/coenzyme/buffer solution on a superabsorbent polymer (SAP), which led to a high stabilization of the enzyme and coenzyme system in the organic solvent. This immobilization technique has meanwhile proven its potential in several other applications also with other enzymes. The new catalyst is especially designed for organic chemists to make enzymatic reductions easily available. We put a Rselective ADH (from Lactobacillus brevis) and a S-selective ADH (from Thermoanaerobicum sp.) and its coenzymes (NADPH) on SAP and created two new unique catalysts, Chiralidon ® -R and Chiralidon ® -S. R and S selectivities refer to the reduction of acetophenone to the (R)-or (S)-1-phenyl ethanol as a standard substrate.