Trehalose with fatty acids

The acetone-soluble fraction was known to contain a large percentage of free fatty acids in addition to the fatty esters. Some of these fatty acids were found by Anderson to be of a type hitherto unknown. In common with the waxes, this fat did not contain any free glycerides. Alkaline hydrolysis of the fat derived from human strain bacilli yielded a water-soluble carbohydrate. This was identified as trehalose by isolation of the crystalline sugar. Corresponding fats isolated from the bovine and avian strains of bacilli were examined. The presence of glycerol could not be detected nor could the carbohydrate components be identified. 

The purification procedure of 6,6 -esters of OMf-trehalose from Coryne-bacterium diphtheria has been modified and the products were analysed by m.s. of the permethylated derivative.The constituent fatty acids have been extensively examined and the detailed structure of the major acids have been confirmed by a variety of techniques. Novel glycolipids in the cord factor fraction from C. diphtheria were a 6,6 -bis(3-oxo-acyl)-o a -D-trehalose and a 6, 6 -mixed ester of aa-trehalose with the 3-oxo-acyl group and a corynomycolic acid. The metabolic implications of these structural studies suggest that condensation of the common fatty acids by a Claisen-like process via the oxo-ester pathway may not be the only pathway for the synthesis of the cord factors. 

An important example of a carbohydrate ester is the so-called cord factor from Mycobacteria spp. This contains an ester of the disaccharide, trehalose, with two molecules of a complex acid, mycolic acid. The latter is a general term embracing a whole series of fatty acids containing 60-90 carbons. They are hydroxy fatty acids which differ in their degree of unsaturation and chain branching (Section 1.9). In the example given in Fig. 2.6 the mycolic acid is the 60-carbon compound found in Mycobacterium smeg-matis. 

Two reports have described similar syntheses of aa-trehalose 6,6 -diesters of either long-chain fatty acids or mycolic acids by the reaction of 6,6 -dideoxy-6,6 -diodo(ordibromo)-2,2, 3,3, 4,4 -hexa-0-trimethylsilyltrehalose with the potassium... 

Perfluoroalkylated fatty acid 6-esters of sucrose and aa-trehalose were prepared by a reaction of sucrose or a,a-trehalose with a perfluoroalkylated acid, Rf(CH2)rtCOOH (Rf = C4F9, C6F 3, or CgFi7, n = 2, 4, 10) in the presence of triphenylphosphine and diisopropyl azodicarboxylate in j/V,iV-dimethylformamide [262]. The surfactants were used to prepare fluorochemical emulsions intended as intravascular oxygen carriers (see Section 10.4). 

The hemolytic activity of the perfluoroalkyiated fatty acid monoesters derived from trehalose or sucrose decreased with increasing length of the perfluo-roalkyl chain and decreased with increasing the hydrocarbon segment. Abouhilale et al. [145] concluded that the most surface-active compounds are the least hemolytic. However, their data appear to suggest also that hemolytic activity is related to lipophilicity, which is reduced by fluorination. 

The sulpholipids (Figure 6.17) consist of trehalose which is sulphated at the 2-position and acylated at several positions on both sugar residues. Instead of mycolic acids, the sulpholipids have a mixture of palmitic add and very long chain (31-46 C) fatty acids with up to 10 methyl branches - known as phthioceranic acids. 

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