A study of ceramides and related compounds.

1. The thesis describes the synthesis of new compounds including both N- and 0-acyl sphingoids, N- and 0-acyl ˜í‚â§-hydroxyaminoacids, related oxazolines, and aminoacid esters and amides of lipids. 2. Some minor lipids chromatographed with ceramides from commercial and fresh biological sources were identified as partially oxidised cerebrosides and monoglycerides respectively. 3. Chromatographic methods (TLC and GLC) were elaborated for the study of sphingolipids with special reference to the study of a) acyl migration; b) ageing; c) stereochemistry. 4. Resolution of groups of erythro and threo sphingoids by TLC and separation of individual diastereoisomers by GLC permitted the assignment of erythro configuration to natural sphingoids of brain. 5. It was shown that synthetic oxazolines derived from sphingoids and containing 0¬¨œÄ and 0¬¨‚â• in the ring were predominantly of the former kind if derived from erythro sphingoids, and of the latter kind if derived from threo sphingoids. 6. All oxazolines, except those derived from erythro sphingenine and containing 0¬¨‚â• in the ring, underwent acid hydrolysis without change of configuration. 7. Synthetic 0-acyl sphingoids readily changed to ceramides in neutral or alkaline media but the conversion of ceramides to 0-acyl isomers could not be brought about by acid; oxazoline intermediates were not found. 8. Neither oxazolines nor 0-acyl sphingoids have been found in fresh or aged ceramide solutions. Changes of ceramides on ageing are ascribed to photo-oxidation. 9. The fatty acid composition of sphingolipids from the milk of Friesian cows was surveyed. 10. The neutral lipids of 68 workers exposed to lead were assayed. 11. Studies of aminoacids in neutral lipid fractions suggest the presence of some covalently bound aminoacid-lipid combinations.