I previously mentioned glutethimide, a close relative of the barbiturates is chiral and that the two enantiomers in vitro activity is quite different. Apropos of this, it is interesting to note that chiral barbiturates ARE known.
It's worth noting that (R) glutethimide is around twice the potency of (S) glutethimide, has a faster onset and an active metabolite which appears to be even more potent. To whit 4-hydroxy glutethimide.
It's worth understanding the history of barbiturates a little bit because the earliest had symmetrical 3,3 di-substitution and that it was the diallyl that proved the most potent. Later examples with different groups at the three position almost always still contain an ethyl or an allyl as one of the two substituents. Later still examples with alkyl or alkynyl halides as one of the 3 substituents were developed.
I find them an interesting class of compound from an academic standpoint but I'm just old enough to have known people who ended up with serious physical dependence. They are certainly a class of compound that a quickly learnt not to mess with.
