Compositions and methods for bioorthogonal surface coating

A compound of formula (I) or a salt thereof:

• wherein:
• L1 is a linker of formula *—X—(Y)m—Z—, wherein * is the bond between X and the carbon marked as **, wherein:
• X is a bond (null), —C(═O)—, —C(═O)NH—, —C(═O)NH(C6-C10 arylene)-, —C(═O)NH(substituted C1-C10 arylene)-, —C(═O)NH(C2-C10 alkenylene)-, or —C(═O)NH(C1-C10 alkylene)-, wherein the substituted C6-C10 arylene comprises at least one substituent independently selected from the group consisting of halogen, —R′, —OR′, and —C(═O)OR′;
• each occurrence of Y is independently selected from the group consisting of —CH2CH2O—, —CH(CH3)CH2O—, —CH2CH(CH3)O—, —C(CH3)2CH2O—, —CH2C(CH3)2O—, —C(CH3)2C(CH3)2O—, —OCH2CH2—, —OCH(CH3)CH2—, —OCH2CH(CH3)—, —OC(CH3)2CH2—, —OCH2C(CH3)2—, —OC(CH3)2C(CH3)2—, —CH2CH2—, —CH(CH3)CH2—, —CH2CH(CH3)—, —C(CH3)2CH2—, —CH2C(CH3)2—, —C(CH3)2C(CH3)2—, with the proviso that O—O bonds are not present;
• Z is selected from the group consisting of optionally substituted C1-C6 alkylene, optionally substituted C6-C10 arylene, and optionally substituted C2-C8 heteroarylene;
• each occurrence of R′ is independently selected from the group consisting of H, optionally substituted C1-C6 alkyl, optionally substituted C2-C6 alkenyl, optionally substituted C6-C10 aryl, and optionally substituted C2-C8 heteroaryl;
• m is selected from the group consisting of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10;
• R1 is selected from the group consisting of H and C1-C6 alkyl;
• each of Ra1, Ra2 and Ra3 is H;
• Rb1 and Rb2 are each independently selected from the group consisting of H and optionally substituted C1-C6 alkyl, wherein at least one of Rb1 and Rb2 is H;
• wherein each optional substituent is independently selected from the group consisting of F, Cl, Br, I, OR, OC(O)N(R)2, CN, NO2, N3, CF3, OCF3, R, N(R)2, SR, S(O)R, SO2R, SO2N(R)2, SO3R, C(O)R, C(O)OR, OC(O)R, C(O)N(R)2, OC(O)N(R)2, N(R)SO2R, N(R)SO2N(R)2, N(R)C(O)OR, N(R)C(O)R, and N(R)C(O)N(R)2;
• and
• each occurrence of R is independently selected from the group consisting of H, C1-C8 alkyl, C3-C8 cycloalkyl, C6-C14 aryl, C1-C8 alkyl(C6-C14 aryl), 5- to 12-membered ring heteroaryl, and C1-C8(5- to 12-membered ring heteroaryl).