Abstract: Provided herein are compounds of formula (II): or a stereoisomer or tautomer thereof, or a pharmaceutically acceptable salt of any of the foregoing, wherein m, n, R2, R3, R5, R6, R7, R8, R9, R10, R11a, R11b, and X are as defined elsewhere herein. Also provided herein are methods of preparing compounds of formula (II). Also provided herein are methods of inhibiting SLC6A19 and methods of treating a SLC6A19-mediated disease, disorder, or condition in an individual in need thereof.