2-[1-[[1-(2-methylpropanoyloxy)ethoxycarbonylamino]methyl]cyclohexyl]acetic acid 2-[1-[[[1-(2-methyl-1-oxopropoxy)ethoxy-oxomethyl]amino]methyl]cyclohexyl]acetic acid 2-[1-[(1-isobutyryloxyethoxycarbonylamino)methyl]cyclohexyl]acetic acid 2-[1-[[1-(2-methylpropanoyloxy)ethoxycarbonylamino]methyl]cyclohexyl]ethanoic acid ASP-8825 GSK-1838262 Gabapentin enacarbil XP-053 XP-13512