Boronic acid derivatives and therapeutic uses thereof

A compound having the structure of formula I:

• or pharmaceutically acceptable salt thereof, wherein:
• G is selected from the group consisting of —H, —NR1R2, —CH2N3, —C(O)NR′ R2, —CH2C(O)NR1R2, —CH2S(O)2NR1R2, —CH2—Y—Z, —CH2—Y—X, and —SR3;
• Y is selected from a group consisting of —S—, —S(O)—, —S(O)2—, —O—, and —NR1—;
• R is selected from a group consisting of —H, —C1-9alkyl, —CR1R2OC(O)C1-9alkyl, —CR1R2OC(O)OC1-9alkyl, and
• R1 and R2 are each independently selected from the group consisting of —H and —C1-4alkyl;
• R3 is —C1-4alkyl;
• R4 is present 1 to 3 times and each R4 is independently selected from the group consisting of —H, —C1-4alkyl, —OH, —OC1-4alkyl, and halogen;
• Z is selected from the group consisting of aryl optionally substituted with C1-4alkyl, amino, hydroxy, or halogen and heteroaryl optionally substituted with C1-4alkyl, amino, hydroxy, or halogen;
• X is selected from the group consisting of —C1-4alkyl, —CH2R5, —CH(R5)2, and —C(R1)3;
• and
• R5 is selected from the group consisting of a halogen, cyano, and azido group.