Freezing effect on chirality amplification of L-asparagine by crystallization of the racemate in preferential condition

The role of freezing in stereoselection by crystallization of a saturated DL-asparagine solution in preferential condition of L-asparagine, has been investigated. To this end, the L-asparagine excess obtained by crystallization and then kept of different lengths of time at n20 degree C in frozen aqueous solution was analyzed. The samples of the yielded materials were derivatised according to Marfey's method. These derivatives were traced and evaluated by RP-HPLC analysis. The relatively best effects appeared after a one day treatment, where the freezing induced asymmetry amplifications and it increased the L-enantiomer excess from 10 mol percent to 34.9, 35.0 and 35.5 mol percent, respectively. Here we provide the first example of the influence of freezing on chirality amplification by preferential crystallization. Also some speculations are made about the implications of our findings in the prebiotic events of L-amino acids.