text: The reaction steps are:
  * hydrogenation of -glucose to -sorbitol, an organic reaction with nickel as a catalyst under high temperature and high pressure.
  * Microbial oxidation or fermentation of sorbitol to -sorbose with acetobacter at pH 4-6 and 30 °C.
  * protection of the 4 hydroxyl groups in sorbose by formation of the acetal with acetone and an acid to Diacetone-L-sorbose (2,3:4,6−Diisopropyliden−α−L−sorbose)
  * Organic oxidation with potassium permanganate (to Diprogulic acid) followed by heating with water gives the 2-Keto-L-gulonic acid
  * The final step is a ring-closing step or gamma lactonization with removal of water.
  * Intermediate 5 can also be prepared directly from 3 with oxygen and platinum
  The microbial oxidation of sorbitol to sorbose is important because it provides the correct stereochemistry.