A general method for the separation of all of the water-soluble steroid and carotenoid precursors formed from mevalonic acid is not available. There are, however, several methods which separate two or more of these compounds. Most of these methods involve the use of an acidic system. For example, the method of choice for the separation of compounds between mevalonic acid and isopentenyl pyrophosphate is ion-exchange chromatography on Dowex 1 formate. A gradient of ammonium formate in formic acid is used in this method (1, 2). Several other acidic systems have been used to separate these compounds by paper chromatography (2-6).
Each of the above methods is effective for the separation of the acidstable compounds between mevalonic acid and isopentenyl pyrophosphate. However, the last three or four water-soluble compounds in the pathway of biosynthesis of squalene and the carotenes are acid-labile. Hence, any general method of separation that includes these compounds must necessarily be performed under neutral or basic conditions.
Correspondingly good methods for the separation of the above acidlabile compounds have not been developed. Basic systems of paper chromatography have been developed to separate the acid-stable compounds (7-S), to separate the terpenyl pyrophosphates from the mevalonic acid phosphorylated derivatives (9), and to separate t'he five-carbon terpenyl pyrophosphates from each other (10). Neither paper nor column chromatographic methods are available to resolve the acid-labile terpenyl pyrophosphates from each other or to separate each of the acid-stable and acid-labile steroid precursors from a mixture.