Enantioselective autocatalysis. V. The spontaneous resolution of tri-o-thymotide.

We have attempted to appraise experimentally the allegation that minute chemical and physical differences due to the parity violating energy difference (PVED) between enantiomers are, after suitable autocatalytic amplification, ultimately responsible for the homochirality of contemporary biomolecules. The autocatalytic amplification technique employed involved the spontaneous resolution under racemizing conditions (SRURC) of a conglomerate during crystallization, and the system studied was the known crystallization of P(+)- or M(-)-tri-o-thymotide (TOT) as its optically active inclusion compound (clathrate) with benzene. Our premise was that if a PVED effect were operative, there should be a strong and consistent bias favoring the crystallization of one enantiomer of the TOT-benzene clathrate. Repetitive preparations of the clathrate, however, yielded crystalline products showing random optical activity. These results thus afford no evidence whatsoever for stereoselective bias due to a PVED, and are in accord with earlier statistical studies demonstrating random SRURC in other conglomerate crystallizations, again indicating the inefficacy of PVEDs to promote a preferred chirality in such systems.