4-butylsulfonyl-N-[2-[4-butylsulfonylbutanoyl(methyl)amino]ethyl]-N-methylbutanamide

N-methyl-N-[2-[methyl(4-oxopentanoyl)amino]ethyl]-4-oxopentanamide

N-methyl-N-[2-[methyl(4-phenylsulfanylbutanoyl)amino]ethyl]-4-phenylsulfanylbutanamide

N-methyl-N-[2-[methyl(4-phenoxybutanoyl)amino]ethyl]-4-phenoxybutanamide

N-methyl-N-[2-[methyl-[4-(4-methylphenyl)sulfanylbutanoyl]amino]ethyl]-4-(4-methylphenyl)sulfanylbutanamide