Novel 3' end caps, 5' end caps and combinations thereof for therapeutic rna

A compound of Formula I or a salt thereof

• wherein Z1 is:
• a cap 0, a cap 1,
• with the proviso that:
• when Z1 is
• cap 0 or cap 1, -A1-R5 and -A3-R8 are not both —OH, and A2 is not null;
• Z2 is null or a linking moiety, selected from the group consisting of —O—, —S—, substituted lower alkyl, substituted aminoalkyl, substituted aryl, substituted heteroaryl, substituted cycloalkyl, substituted cycloalkenyl, substituted heterocyclyl,
• A1 and A3 are independently selected from the group consisting of null, NH, S, and O;
• A2 is null or selected from the group consisting of >CR6R7, >NR6, >NNR6R7, >NOR6, >S, and >O;
• Y is null or a linking moiety selected from the group consisting of substituted lower alkyl, substituted alkenyl, substituted alkynyl, —(CH2)nOR15, —(CH2)nCOOR15, and —(CH2)nC(O)NR12;
• R1 is selected from the group consisting of H, substituted cycloalkyl, substituted cycloalkenyl, substituted aryl, substituted heteroaryl, and substituted heterocyclyl;
• R2 is selected from the group consisting of H, —OH, substituted alkyl, —C(O)NR12R13 and —NR12R13;
• R5, R6, and R8 are independently selected from the group consisting of H, substituted alkyl, polyamine, PEGs, —(CH2)n1NR12R13, —(CH2)n1NR14C(O)R15, —(CH2)n1OR, —(CH2)n1C(O)OR, —(CH2)n1C(O)R15, —(CH2)n1C(O)NR12R13, —O—(CH2)n3—C(O)—(NR12)2—C(O)—X2, —O—(CH2)n3—C(O)—[NR12—C(O)—(CH2)n3]1-3—X2, or R6 and R8 together form a ring that is substituted and contains 10-80 ring atoms in which 10-40 ring atoms can be hetero atoms, or R6 and R7 together form a 3-8 membered ring that is substituted and in which 1 to 6 ring atoms can be hetero atoms;
• R7, R11, R12, R13, R14, R15 and R16 are independently selected from the group consisting of H, substituted lower alkyl, and substituted acyl;
• R9 is selected from the group consisting of H and substituted lower alkyl;
• R10 is selected from the group consisting of H, —NR12R13, and —OR16;
• n is 1 to 4;
• n1 is zero to 10;
• n2 is 1 to 12;
• n3 is 1 to 8;
• X is selected from the group consisting of O, S, NH, and substituted alkanediyl;
• X1 is selected from the group consisting of
• R3 and R4 are independently selected from the group consisting of H and —OR16, or R3 and R4 together form O-Q-O;
• Q is selected from the group consisting of —CH2— and —C(Me)2-;
• X2 is selected from the group consisting of affinity moiety and detection moiety, and
• Xn is a nucleobase.