A new route to deoxythiosugars based on aldolases has been developed. Representative syntheses of several thioketoses and 1-deoxy-5-thio-D-glucose, 1-deoxy-5-thio-D-galactose, 1-deoxy-5-thio-L-altrose, 1-deoxy-5-thio-D-mannose, 1-deoxy-5-thio-L-mannose, and 2-deoxy-5-thio-D-ribose are illustrated with the use of fructose 1,6-diphosphate aldolase, fuculose 1-phosphate aldolase, rhamnulose 1-phosphate aldolase, and 2-deoxyribose 5-phosphate aldolase in reaction with an appropriate thioaldehyde, followed by reduction with triethylsilane in the presence of BF3.Et(2)O.