A compound having the structure wherein R is, for example, Y is selected from the group consisting of 1) R5, 2) —C(R1R2) (C(R3R4))0-1Y1R5, and 3) —C(R1R2)—O—Y1R5； R1, R2, R3 and R4 are independently selected from the group consisting of hydrogen and C1-4 alkyl； R5 is； Y1 is selected from the group consisting of C(O)—O— and P(O)(OR6)—O—； and R6 is hydrogen or CH3, or a pharmaceutically acceptable salt thereof, and methods of using the compounds for treating hypertension.
