Chapter 2 

 ASCORBIC ACID 



Page 



I. Nomenclature ami Forimilas 170 



II. Chemistry 180 



A. Isolation of L-Ascorl)ic Acid 180 



B. Natural Occurrence of L-Ascorhic Acid 182 



C. Chemical Nature and Constitution of L-Ascorbic Acid 183 



D. Synthesis of l- Ascorbic Acid 188 



1. Method 1. Addition of Hydrogen Cyanide to a Glycosone and 

 Conversion of the Intermediate Iminoascorbic Acid into l-As- 

 corbic Acid by Hj'drol^sis 188 



2. Method 2. Simultaneous Lactonization and Isomerization of an 

 Appropriate 2-Keto Acid or Ester 191 



3. Method 3. Benzoin Condensation of Sugars with Ethyl Glyoxyl- 



ate or Ethyl Mesoxalate 1'^' 



4. Method 4. Claisen Condensation of Esters of Hydroxy Acids . . 197 



E. Structure and Antiscorbutic Activity of Analogs of L-Ascorbic Acid. 198 



F. Derivatives of L-Ascorbic Acid 202 



1. Dehydroascorbic Acid 202 



2. Acyl and Aryl Derivatives 205 



3. Ethers. . ] 205 



III. Industrial Preparation 209 



IV. Biochemical Systems 211 



A. Synthesis of Ascorbic Acid 211 



1. Site of Formation 212 



2. Formation from Sugars 213 



3. Dependence of Biosynthesis on External Factors 217 



4. Synthesis of Ascorbic Acid in Vitamin-Deficient Animals . . . 222 



5. Glucoascorbic Acid and Synthesis of Ascorbic Acid 223 



B. Function of Ascorbic Acid in Biochemical Systems 224 



1. Systems Catalyzing the Oxidation of Ascorbic Acid 224 



2. Enzymic Systems Associated with the Reduction of Dehydroas- 

 corbic Acid 228 



3. Ascorbic Acid and the Metabolism of Tyrosine 236 



4. Action of Ascorbic Acid on Enzymes 238 



5. Ascorbic Acid and Phosphatase 239 



6. Ascorbic Acid and Carbohydrate Metabolism 241 



7. Ascorbic Acid and the Synthesis of the Leiiconostoc cilrovorum 

 Factor 241 



8. Ascorbic Acid and the Formation of Intracellular Sul)stances and 

 Collagen 242 



V. Estimation 242 



A. Biological Methods 242 



177 



