Coupling agents for peptide synthesis

A compound or salt consisting of an anion and cation, wherein the compound or the cation of the salt is of the formula

• wherein
• A is CR26;
• D is CR27 or N;
• E is CR28 or N;
• G is CR29 or N;
• R26, R27, R28 and R29 are independently hydrogen, a lower alkyl group or an electron donating group;
• wherein one of D, E and G, is N and the others are carbon;
• Y1 is N;
• Q1 is N;
• R14 is a positively charged electron withdrawing group,
• SO2R17, lower alkyl carbonyl, lower arylalkyl carbonyl, aryl carbonyl, lower alkyl aryl, or BLK1-AA1
• R17 is aryl, aryl lower alkyl or lower alkyl;
• AA1 is an amino acid or peptide less a hydrogen atom on the N-terminus and an OH on the C-terminus;
• BLK1 is an amino protecting group,
• R10 is OR12, lower alkyl, aryl, aryl lower alkyl, lower cycloalkyl, lower cycloalkyl lower alkyl, heterocyclic, heterocyclic lower alkyl, lower cycloalkenyl, or lower cycloalkenyl lower alkyl;
• R11 is OR13, lower alkyl, aryl, aryl lower alkyl, lower cycloalkyl, lower cycloalkyl lower alkyl, heterocyclic, heterocyclic lower alkyl, lower cycloalkenyl or lower cycloalkenyl lower alkyl;
• and R10 and R11 may optionally be connected by a bridging group selected from the group consisting of O, S, NR30, or (CHR30)m, wherein each R30 is independently lower alkyl or hydrogen and m is 1-3;
• and
• R12 and R13 are independently lower alkyl, lower cycloalkyl, lower cycloalkyl lower alkyl, heterocyclic, heterocyclic lower alkyl, lower cycloalkenyl or lower cyclalkenyl lower alkyl;
• ring A1 and ring B are independently an aromatic ring containing 6 to 14 ring carbon atoms or cycloalkenyl or cycloalkyl, each containing 5 to 14 ring carbon atoms, and
• Rb1, Rc1, Rb2, Rc2 are independently hydrogen, lower alkyl or electron donating group;
• T is CHR31, O, S or NR30;
• and
• R31 is hydrogen or lower alkyl.