Controlling solvates of phenylalanine

Phenylalanine is an α-amino acid with the formula C6H5CH2CH(NH2)COOH. It is an essential amino acid, meaning that the body needs it for health, but cannot produce it. However, it is found naturally in the breast milk of mammals. Phenylalanine is used in the manufacture of food and drink products and sold as a nutritional supplement for its reputed analgesic and antidepressant effects. It is a direct precursor to the neuromodulator phenylethylamine, a commonly used dietary supplement.

Phenylalanine is found in 3 forms: L-phenylalanine, the natural form found in proteins; D‑phenylalanine (a mirror image of L-phenylalanine that is made in a laboratory), and DL‑phenylalanine, a combination of the 2 forms. Each of these forms has its own uses.

As phenylalanine is an important nutritional supplement, easy processing of the compound is of major importance. Therefore it is important to control the crystal structure. As it happens, phenylalanine makes a solvate with water: phenylalanine monohydrate. The crystals of this hydrate are very long needles. For processing this is highly undesirable, since it easily clogs up filters. Instead anhydrous phenylalanine with plate-like crystals is the more desirable form.

The goal of this project is to control the crystallization of phenylalanine so that the anhydrous form can be obtained. There are several ways of controlling solvate formation, several of which will be investigated and compared.