Derivatization of prostaglandins and related compounds to (methoxime) alkyl ester alkyl ether derivatives for gas chromatographic analysis

Rapid and convenient methods are described for the exhaustive derivatization of carbonyl, carboxyl and hydroxyl groups of prostaglandins and related compounds to methoxime, alkyl ester and alkyl ether compounds respectively. Optimal reaction conditions were established for each group. The reactions were carried out in polar aprotic solvents. Alkyl ester alkyl ether derivatives were obtained quantitatively and rapidly in one step with n-alkyl (C1-C4) halides in the presence of sodium hydroxide. Methyl ester methyl ether derivatives have the highest volatility, but propyl ester propyl ether derivatives improved the separation of complex mixtures. The carbonyl group sometimes induced side-products, so the carbonyl group was converted into methoxime. Methoximation was achieved quantitatively by using methoxylamine in the presence of hydrochloric acid or sodium hydroxide, followed by alkylation in same reaction medium. Methoximation gave syn- and anti-isomers, which were separated chromatographically, decreasing the resolution for complex samples.