Diasterio- und enantioselektive Reduktion von β-Ketoestern mit Cyclopentanon-, Cyclohexanon-, Piperidon- und Tetralon-Struktur durch nicht fermentierende Bäcker-Hefe
✍ Scribed by Dieter Seebach; Silvio Roggo; Thomas Maetzke; Hans Braunschweiger; Jacques Cercus; Manfred Krieger
- Publisher
- John Wiley and Sons
- Year
- 1987
- Tongue
- German
- Weight
- 742 KB
- Volume
- 70
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Under 'non-fermenting' conditions, i.e. in tap water, in the absence of nutrients, baker's yeast (25-380 g/g of substrate, aerobic) reducesb-keto esters such as those mentioned in the title with better selectivity than under the normally employed 'fermenting' conditions (sugar and nutrients, CO, development). With the B-keto esters containing the tetralone substructure, large amounts 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 configurations of most products (16-24) is established. Generally, the (R)-b-keto ester is reduced faster than the (S)-enantiomer (the two esters are in equilibrium under the reaction conditions), and the hydride transfer takes place preferentially from the diastereotopic Re-face. The B-hydroxy esters thus available are useful starting materials for syntheses of enantiomerically pure compounds (EPC).