30Four enzymes have been discovered in Japan that catalyse the oxidation of alditols (sugaralcohols, eg Xylitol – see figure below) to ketoses (sugar ketoses). These enzymes are specific for certain

substrates, recognising particular structural motifs, as shown in the scheme below. Now consider the following scheme involving D-glucose 1. a. For compound 2, determine the absolute configurations R or S of all the stereogenic centres.[6] p. Suggest the structure of product 3. c. Suggest an enzyme to achieve the transformation of 2 to 4. d. Identify which of the following words describe(s) the relationship between ketones 3 and 4? enantiomers, diastereomers, epimers, anomers, identical [21 Ketose 4 can also be obtained from D-galactose by exploiting a fifth enzyme, enzyme E which catalyses the following reactions Now consider the following reaction scheme, which involves D-galactitol 6 (obtained by reduction of D-galactose) e. Suggest a structure for product 5, and identify the enzyme that catalyses its formation from D-galactitol Determine the structure of ketose 8. g. How are D and L- galactitol related to each other?