Enzymatic and organocatalyzed asymmetric aldolization reactions for the synthesis of thiosugar scaffolds

International audienceWe studied the synthesis of original thiosugar scaffolds by enantioselective aldolization. L-Proline-catalyzed C-C bond formation was the key step in the synthesis of L-erythro-thioketoses (3S,4R), whereas fructose-6-phosphate aldolase-catalyzed reactions yielded the D-threo-thioketose series (3S,4S). By the organocatalytic approach, 5-thio-L-ribulofuranose (1) and 5-deoxy-6-thio-L-psicopyranose (2) were obtained in satisfactory overall yields from 2-haloacetaldehydes, whereas 5-thio-D-xylulofuranose (3) was synthesized in 50 % overall yield by an enzymatic aldolization reaction in only two steps from the same starting material