Inhibitors of the renal outer medullary potassium channel

A compound having structural Formula I:

• or a pharmaceutically acceptable salt thereof wherein:
• Z1 is
• Z2 is
• R1 is —H, —CH3, —CF3, —CHF2, —CH2F or —CH2OH;
• R2 is —H, oxo (═O) or —C1-6alkyl;
• R4 is —H, —OH, oxo or —C1-6alkyl;
• provided that when R4 is —OH or oxo, then R2 is not oxo;
• R3 and R5 are each independently —H or —C1-6alkyl;
• provided that R3 is absent when R2 is oxo, and R5 is absent when R4 is oxo;
• R1a is —H, halo or —C1-3alkyl;
• R1b is —H, halo, —C1-3 alkyl, —O—C1-3 alkyl or —COOC1-3alkyl;
• one of R2a and R2b is —CN and the other is —H or —C1-3alkyl;
• one of R2c and R2d is —SO2—C1-3alkyl and the other is —H or —C1-3alkyl;
• X1, X2, X3 and X4 are each independently CH or N, provided that only one of X1, X2, X3 or X4 is N;
• X5, X6 and X7 are each independently CH or N, provided that only one of X5, X6 or X7 is N;
• and
• Ra and Rb are each independently —H, halo, —C1-3alkyl, —O—C1-3alkyl or —COOC1-3alkyl.