Chiral separation with dipeptide-terminated polymeric surfactants: The effect of an extra heteroatom on the polar head group

Chiral recognition of two binaphthyl derivatives and three benzodiazepines were studied by use of polymeric surfactants in electrokinetic chromatograp hy. four specific dipeptide terminated (multichiral) micelle polymers were synthesized for this study. These include poly (sodium-N-undecanoyl-L-alany l-leucinate)-(poly L-SUAL), poly (sodium-N-undecanoyl-L-valyl-leucinate) (p oly L-SUVL), poly (sodium-N-undecanoyl-L-seryl-leucinate) (poly L-SUSL), an d poly(sodium-N-undecanoyl-L-threonyl-leucinate) (poly L-SUTL). In addition to the chiral separation study, the physicochemical properties (critical m icelle concentration and specific rotation) of each polymer were investigat ed. The molecular weights of the various dipeptide-terminated micelle polym ers were determined using analytical ultracentrifugation. These dipeptide-t erminated micelle polymers were designed to study the effect of the extra h eteroatom at the polar head group of the micelle polymer (i.e., poly L-SUSL compared to poly L-SUAL and poly L-SUTL compared to poly L-SUVL) on the en antiomeric separation of the binaphthyl derivatives and benzodiazepines. Th e synergistic effect of three chiral centers (poly L-SUTL) provided improve d resolution over that of two chiral centered dipeptide-terminated micelle polymer in the case of (+/-)-temazepam, (+/-)-oxazepam, (+/-)binaphthol, an d (+/-)-binaphthol phosphate. The chiral recognition mechanisms in these ca ses were additionally controlled by the presence of the extra heteroatom lo cated on the polar head group of the micelle polymers.