Diasterio‐ und enantioselektive Reduktion von β‐Ketoestern mit Cyclopentanon‐, Cyclohexanon‐, Piperidon‐ und Tetralon‐Struktur durch nicht fermentierende Bäcker‐Hefe

Diastereo- and Enantioselective Reduction of beta;-Keto Esters Derived from Cyclopentanone, Cyclohexanone, Piperidone and Tetralone by ‘Non-fermenting’ Baker's Yeast Under ‘non-fermenting’ conditions, i.e. in tap water, in the absence of nutrients baker's yeast (25–380 g/g of substrate, aerobic) reduces β-keto esters such as those mentioned in the title with better selectivity than under the normally employed ‘fermenting’ conditions (sugar and nutrients, CO2 development). With the β- keto esters containing the tetralone substructure, large amount of yeast are required (250–380 g/g); the substrate disappears in the biomass, and the desired reduction product can be extracted after reaction times of up to a week at 30°. The configuration of most products(16–24) is established. Generally, the (R)-β-keto ester is reduced faster than the (S)-enantiomer (the two esters are in equilibrium under the reactio conditions), and the hydride transfer takes place preferentially from the diastereotopic Re-face. The β-hydroxy esters thus available are useful starting materials for syntheses of enantiomerically pure compounds (EPC).