Condensation Products of Lipoids and Chemo Immunity. I. Synthesis of Azo Derivatives of Cholesterol Aryl Esters

It has been proposed by Forssman, 1 Meyer, 2 Wernicke and Sordelli, 3 Taniguchi, 4 Landsteiner, 5 and Landsteiner and Simms 6 that some heterogenetic antigens may be composed of 2 chemically different substances, one being represented by a lipoidal substance containing the specific group but possessing no antigenic properties. The other component is of the nature of a protein. Since Landsteiner and Simms 6 reported investigations only with simple mixtures of these 2 systems, and Klopstock and Selter 7 those with mixtures of lecithin and diazotised atoxyl, it was of interest to study the possibility of chemically combining lipoidal substances with proteins and their degradation products to obtain a product of a definite entity which then could be used for immunological experiments. From a different aspect combination of lipoidal substances with proteins or their degradation products is interesting because of the colloidal nature of such condensations in an aqueous system. Such a physical state of the antigen is claimed to be important in immunity reactions.

The present report deals with experiments in which we prepared condensation products of cholesterol derivatives with certain amines, amino acids, and peptides. There are also indications of successful condensations with proteins.

Cholesterol, especially purified over the dibromide, was esterified with 4-nitrobenzoylchloride. The ester obtained was reduced with a Pt-catalyst as described by Shriner and Ko 8 to form the corresponding cholesteryl-4-aminobenzoate. For condensation with the above mentioned substances (amines, amino acids, peptides, etc.), diazotisation of the amino benzoyl ester was studied. A number of difficulties were encountered. It was found, for example, that while the hydrochloride of the cholesteryl-4-aminobenzoate can also be prepared by carefully grinding it with an excess of conc.