Residue fatty-ester synthesis

Acetyl-CoA is the hub of carbohydrate metabolism and has a central position in overall metabolism. Products of carbohydrate, fat and protein metabolism are channeled via acetyl-CoA into oxidative degradation in the tricarboxylic acid cycle. The acetyl residue is used in the synthesis of esters and amides (e.g. acetylcholine, Af-acetylglucosamine, N-acetylgluta-mate). Acetyl-CoA is also the starting point for iso-prenoid synthesis via mevalonic acid and for fatty acid synthesis. 

Amide bonds are found in many proteins. One is the acyl carrier protein of Escherichia coli (see 90), which contains the peptide backbone, and a 4 -phosphopantetheine unit (in violet in the illustration) is attached to a serine residue. Note the amine bonds in the pantothenic acid unit and also the 0-P=0 unit, which is a phosphate ester (an ester of phosphoric acid). An acyl carrier protein is involved in fatty acid synthesis, linking acetyl and malonyl groups from acetyl coenzyme A and malonyl coenzyme A to form P-keto acid acyl carrier protein (abbreviated as ACP). The widely utilized acetyl CoA is an ester (91) attached to coenzyme A. Acetyl CoA is a key intermediate in aerobic intermediary metabolism of carbohydrates, lipids, and some amino acids. 

Naimochelin C (Fig. 15, 54) from the myxobacterium Nannocystis exedens contains two L-Lys and two ( )-cinnamic acid units. The reported mono- and di-methyl esters (nannochelin B and A) may be artifacts from the work-up (198). A synthesis is described (29) (see Sect. 8.4). The ochrobactins (Fig. 15,55) isolated from the sea-shore bacterium Ochrobactrum sp. (214) with the spacer L-lysine are membrane active due to the fatty acid residues (saturated Cg and (2 )-unsaturated Cg and Cio) cf. lipopeptidic siderophores in Sect. 2.8. 

A major drawback of the sucrose ester surfactants is the difficulty of synthesis due to the lack of mutual solubility between the sugar and the hydrophobic components, usually fatty acids. To obtain a commercially viable process, a good solvent for all components such as dimethylsulfoxide (DMSO) must be used. To make the final product meet FDA standards, the level of residual DMSO must be extremely low, requiring rigorous purification, implying high production costs. Nevertheless, the advantages of the family of products has led to a their commercial productions in limited quantities. 

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