Patent ID: 8901164

Claim:
A compound of formulas 1a-1c: wherein: R 1 , R 4 and R 5 can be alkyl, cycloalkyl, alkenyl, alkynyl, aryl, CH 2 -aryl, heteroaryl, CH 2 -heteroaryl, CH 2 CO 2 H, CH 2 CH 2 CO 2 H, CH 2 OH, (CH 2 ) 4 NH 2 , (CH 2 ) 3 N═C(NH 2 ) 2 , O-alkyl, O-cycloalkyl, O-alkenyl, O-alkynyl, O-aryl, O—CH 2 -aryl, O-heteroaryl, O—CH 2 -heteroaryl, O—CH 2 CO 2 H, O—CH 2 CH 2 CO 2 H, O—(CH 2 ) 2 OH, O—(CH 2 ) 4 NH 2 , or O—(CH 2 ) 3 N═C(NH 2 ) 2 ; R 2 can be alkyl, cycloalkyl, alkenyl, alkynyl, aryl, CH 2 -aryl, heteroaryl, CH 2 -heteroaryl, O-alkyl, O-cycloalkyl, O-alkenyl, O-alkynyl, O-aryl, O—CH 2 -aryl, O-heteroaryl, O—CH 2 -heteroaryl, NH-alkyl, NH-cycloalkyl, NH-alkenyl, NH-alkynyl, NH-aryl, NH—CH 2 -aryl, NH-heteroaryl, NH—CH 2 -heteroaryl, CO-alkyl, CO-cycloalkyl, CO-alkenyl, CO-alkynyl, CO-aryl, CO—CH 2 -aryl, CO-heteroaryl, CO—CH 2 -heteroaryl, CO 2 -alkyl, CO 2 -cycloalkyl, CO 2 -alkenyl, CO 2 -alkynyl, CO 2 -aryl, CO 2 —CH 2 -aryl, CO 2 -heteroaryl, or CO 2 —CH 2 -heteroaryl; R 3 can be alkyl, cycloalkyl, alkenyl, alkynyl, aryl, CH 2 -aryl, heteroaryl, CH 2 -heteroaryl, CO-alkyl, CO-cycloalkyl, CO-alkenyl, CO-alkynyl, CO-aryl, CO—CH 2 -aryl, CO-heteroaryl, CO—CH 2 -heteroaryl, CO 2 -alkyl, CO 2 -cycloalkyl, CO 2 -alkenyl, CO 2 -alkynyl, CO 2 -aryl, CO 2 —CH 2 -aryl, CO 2 -heteroaryl, CO 2 —CH 2 -heteroaryl, COCO 2 H, COCO 2 -alkyl, COCO 2 -cycloalkyl, COCO 2 -alkenyl, COCO 2 -alkynyl, COCO 2 -aryl, COCO 2 —CH 2 -aryl, COCO 2 -heteroaryl, COCO 2 —CH 2 -heteroaryl, SO 2 -alkyl, SO 2 -cycloalkyl, SO 2 -alkenyl, SO 2 -alkynyl, SO 2 -aryl, SO 2 —CH 2 -aryl, SO 2 -heteroaryl, or SO 2 —CH 2 -heteroayl; and X═H or OCH 2 CO 2 H, wherein the latter functionality serves as a solubilizing group.