(a) The enzyme KDPG aldolase catalyzes the aldol addition reaction between pyruvate and

Chapter 22, Problem 22.23

(choose chapter or problem)

(a) The enzyme KDPG aldolase catalyzes the aldol addition reaction between pyruvate and glyceraldehyde-3-phosphate. HO H H O 2O3PO C (R)-glyceraldehyde3-phosphate (G3P) pyruvate O O H3C O C C 3-keto-2-deoxy-6- phosphogluconate (KDPG) The reaction is known to involve the formation of an imine (Schiff base) between a lysine residue of the enzyme and pyruvate. Give the product of the reaction (KDPG) and outline a curved-arrow mechanism, assuming acids and bases are present as needed. (The stereochemistry of the asymmetric carbons is the same as in Eq. 22.57.) (b) The product of this reaction exists as two diastereomeric cyclic acetals. Give their structures.