Chemo‐enzymatische Synthese von Kohlenhydraten: Die Herstellung von L ‐Xylose und 2‐Desoxy‐ L ‐ xylo ‐hexose

Chemo‐Enzymatic Synthesis of Carbohydrates: The Preparation of L ‐Xylose and 2‐Deoxy‐ L ‐ xylo ‐hexose A synthetic approach to L ‐xylose ( 6 ) and 2‐deoxy‐ L ‐ xylo ‐hexose ( 8 ) has been developed. The strategy utilizes achiral starting materials and employs two enzymatic reactions to introduce the desired chiral centers. Rabbit muscle aldolase (RAMA)‐catalyzed condensation of (3‐phenylthio)propanal ( 1 ) with dihydroxyacetone phosphate (DHAP) affords the C‐6 skeleton 2 with D ‐ threo configuration between C‐3 and C‐4. Diastereoselective reduction of 2 with sorbitol dehydrogenase (SDH) introduces the final stereocenter of the tetrahydroxy derivative 3 . After oxidation of sulfide 3 to the corresponding diastereotopic sulfoxides 4 , L ‐xylose ( 6 ) is obtained by thermal elimination of phenylsulfenic acid followed by ozonolysis. 2‐Deoxy‐ L ‐ xylo ‐hexose ( 8 ) is yielded from 4 by a Pummerer rearrangement and subsequent reductive deprotection (DI‐BAL‐H) of the rearrangement product 7 .