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

Abstract

Diastereo‐ and Enantioselective Reduction of beta;‐Keto Esters Derived from Cyclopentanone, Cyclohexanone, Piperidone and Tetralone by ‘Non‐fermenting’ Baker's YeastUnder ‘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).