Tumors can be selectively targeted via compounds provided herein according to the formula, or a pharmaceutically acceptable salt thereof, wherein RA and RB are as defined herein. Tumors can be imaged or targeted for therapeutic treatment using compounds described herein where at least one RA or at least one RB group comprises a imaging agent, a therapeutic agent, or a member of a specific binding pair which can be associated with a secondary imaging agent, such as a microbubble for ultrasonic imaging.