Hydrolysis, acid, carbohydrates amides

Experiments on the respiration of detached leaves not only illustrate the control of respiration rate by availability of respiratory substrates but illustrate very clearly that not only carbohydrates but also proteins may be respired. This protein respiration involves protein hydrolysis to yield amino acids and amides, deamination of these amino acids and subsequent decarboxylation (leading to carbon dioxide release) and oxidation of the resulting organic acids. 

A stereochemical control of the Ugi reaction can be effected with carbohydrates as chiral templates (e.g. tetrakis(O-pivaloyl)galactosylamine), which gives rise to easily separable amides. From these a variety of non-natural amino acids can be derived after acidic hydrolysis. The Passerini reaction, related to the Ugi rearrangement, gives a-hydroxyamides. A modification of this reaction using titanium tetrachloride gives a-branched amides in high yields via C-metalated imidoyl chlorides (equation 38). 

In all forms of digestion (whether of proteins, carbohydrates, or fats), larger molecules are broken down into smaller molecules by a reaction with water in which a water molecule is split in two, each part joining a different product molecule. This type of reaction is called hydrolysis. Remember that proteins are long chains of amino acids linked together by amide functional groups called peptide bonds. When protein molecules are digested, a series of hydrolysis reactions convert them into separate amino acids. 

Carbohydrates are hydrolyzed by the action of acids. Since polymer acids are efficient catalysts for the hydrolysis of esters and amides, attempts have been made to use them for the hydrdysis of carbohydrates. Kern and co-workers (36) found that tlw catalytic activity of poly(styrenesulfonic acid) 2 in the hydrolysis of sucrose 25 was comparable to that of sulfuric acid. A sulfonated polystyrene gel (cation exchange resin) was sli tly more effective (37). 

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