The present invention relates to compounds which comprise a nitrogen-containing ring scaffold substituted by an R1 alkyl units selected from the group consisting of C1–C12 linear or branched alkyl, C3–C8 cyclic alkyl, C2–C12 linear or branched alkenyl, or haloalkyl, for example, the 2-keto-3-alkylpiperazines having the formula: wherein R is selected from the group consisting of phenyl, 3-fluorophenyl, 4-fluorophenyl, 3,5-difluorophenyl, and 4-chlorophenyl; R1 is selected from the group consisting of methyl, ethyl, propyl, iso-propyl, butyl, iso-butyl, sec-butyl, tert-butyl, cyclopropyl, cyclopropylmethyl, cyclopentyl, cyclopentylmethyl, cyclohexyl, cyclohexylmethyl, benzyl, allyl, 1-methylallyl, 2-methylallyl, but-2-enyl, and propargyll; R7a is selected from the group consisting of hydrogen, —CO2H, —CONH2, —CONHCH3, and —CON(CH3)2; R8 is benzyl, substituted benzyl, or naphthalen-2-ylmethyl.