Preparation of Parinaric Acid Derivatives

This chapter describes the preparation of parinaric acid derivatives. The lysolecithin obtained from phospholipase A2 treatment of egg phosphatidylcholine is dried in a flask over night under vacuum over P₂O₅. Freshly distilled anhydrous chloroform, 5 ml, is added and the solution is treated with half of a solution, containing 469 mg of anhydrous parinaric acid and 274 mg of carbonyldiimidazole in 5 ml of chloroform. The reaction mixture is stirred under argon for 3 h at room temperature, and then the remaining half of the parinaroylimidazole solution is added. trans-Parinaroylhydroxysuccinimide ester, in 8.6 ml of tetrahydrofuran, is mixed with an aqueous solution containing glucosamine hydrochloride and NaHCO₃. N-trans-parinaroylglucosamine is slightly soluble in methanol and more soluble in dimethyl sulfoxide (DMSO). A stock solution is prepared by dissolving the solid in DMSO and methanol. The Morgan-Elson method for testing of N-acylhexosamines is used, and the characteristic absorptions at 544 and 585 nm are observed. The Morgan-Elson test for N-acylhexosamine is positive. The heating time for this compound in the Morgan-Elson reaction is 6 min, and it gives the same extinction coefficients as N-acetylglucosamine.