Reversible covalent linkage of functional molecules

1. A method for linking a compound of formula F 1 —H, wherein F 1 is a first functional moiety which, together with the H-atom to which it is attached, contains an SH group, to a second functional moiety of formula F 2 with a reagent which is a compound of formula (Ia):

wherein:

X and X′ each represent oxygen;

either:

R 3 and R 3 ′ together form a group of formula —N(R 33 ′), wherein R 33 ′ represents a hydrogen atom or a group of formula Y, Nu,

-L(Z) n or IG; or

R 3 and R 3 ′ together form a group of formula —N(R 33 ′)—N(R 33 ′)—, wherein each R 33 ′ is the same or different and represents a hydrogen atom or a group of formula Y, Nu, -L(Z) n or IG;

R 2 represents a hydrogen atom or a group of formula Y, Nu, -L(Z) n or IG;

each group of formula Y is the same or different and represents an electrophilic leaving group;

each group of formula Nu is the same or different and represents a nucleophile selected from —OH, SH, —NH 2 and —NH(C 1-6 alkyl);

each group of formula L is the same or different and represents a linker group;

each group of formula Z is the same or different and represents a reactive group attached to a group of formula L which is capable of reacting with a compound containing a second functional moiety such that said second functional moiety becomes linked to said group of formula L;

n is 1, 2 or 3; and

each group of formula IG is the same or different and represents a moiety which is a C 1-20 alkyl group, a C 2-20 alkenyl group or a C 2-20 alkynyl group, which is unsubstituted or substituted by one or more substituents selected from halogen atoms and sulfonic acid groups, and in which (a) 0, 1 or 2 carbon atoms are replaced by groups selected from C 6-10 arylene, 5- to 10-membered heteroarylene, C 3-7 carbocyclylene and 5- to 10-membered heterocyclylene groups, and (b) 0, 1 or 2 —CH 2 — groups are replaced by groups selected from —O—, —S—, —S—S—, —C(O)— and —N(C 1-6 alkyl)- groups, wherein:

(i) said arylene, heteroarylene, carbocyclylene and heterocyclylene groups are unsubstituted or substituted by one or more substituents selected from halogen atoms and C 1-6 alkyl, C 1-6 alkoxy, C 1-6 alkylthiol, —N(C 1-6 alkyl)(C 1-6 alkyl), nitro and sulfonic acid groups; and

(ii) 0, 1 or 2 carbon atoms in said carbocyclylene and heterocyclylene groups are replaced by —C(O)-groups;

and

either:

the first functional moiety or the second functional moiety is a protein which is an antibody or antibody fragment, and the other of the first functional moiety and the second functional moiety is a drug; or

the first functional moiety or the second functional moiety is a polymeric moiety selected from peptides, proteins, polysaccharides, polyethers, polyamino acids, polyvinyl alcohols, polyvinylpyrrolidones, poly(meth)acrylic acid, polyurethanes and polyphosphazenes, and the other of the first functional moiety and the second functional moiety is a drug;

wherein the method comprises attaching the F 1 to the compound of formula (Ia) via nucleophilic attack of the SH group in the compound of formula F 1 —H at the 2-position of the compound of formula (Ia), such that the group Y at the 2-position is replaced by the group F 1 ; and the method comprises attaching F 2 by electrophilic addition across the carbon-carbon double bond between the 2- and 3-positions of the compound of formula (Ia) or by reaction with a reactive group on the compound of formula (Ia) that is capable of reacting with F 2 .

2. A method according to claim 1 , wherein Y is a halogen atom or a triflate, tosylate, mesylate, N-hydroxysuccinimidyl, N-hydroxysulfosuccinimidyl, C 1-6 alkythiol, 5- to 10-membered heterocyclylthiol, C 6-10 arylthiol, C 3-7 carbocyclylthiol, —OC(O)CH 3 , —OC(O)CF 3 , phenyloxy, —NR—R y R z + or —PR—R y R z + group, in which R x , R y , and R z are the same or different and are selected from hydrogen atoms and C 1-6 alkyl and phenyl groups.

3. A method according to claim 1 , wherein L represents a moiety which is a C 1-20 alkylene group, a C 2-20 alkenylene group or a C 2-20 alkynylene group, which is unsubstituted or substituted by one or more substituents selected from halogen atoms and sulfonic acid groups, and in which (a) 0, 1 or 2 carbon atoms are replaced by groups selected from

C 6-10 arylene, 5- to 10-membered heteroarylene, C 3-7 carbocyclylene and 5- to 10-membered heterocyclylene groups, and (b) 0, 1 or 2 —CH 2 — groups are replaced by groups selected from —O—, —S—, —S—S—, —C(O)— and —N(C 1-6 alkyl)- groups, wherein:

(i) said arylene, heteroarylene, carbocyclylene and heterocyclylene groups are unsubstituted or substituted by one or more substituents selected from halogen atoms and C 1-6 alkyl, C 1-6 alkoxy, C 1-6 alkylthiol, —N(C 1-6 alkyl)(C 1-6 alkyl), nitro and sulfonic acid groups; and

(ii) 0, 1 or 2 carbon atoms in said carbocyclylene and heterocyclylene groups are replaced by —C(O)-groups.

4. A method according to claim 1 , wherein L represents a moiety which is an unsubstituted C 1-6 alkylene group, C 2-6 alkenylene group or C 2-6 alkynylene group, in which (a) 0 or 1 carbon atom is replaced by a group selected from phenylene, 5- to 6-membered heteroarylene, C 5-6 carbocyclylene and 5- to 6-membered heterocyclylene groups, wherein said phenylene, heteroarylene, carbocyclylene and heterocyclylene groups are unsubstituted or substituted by one or two substituents selected from halogen atoms and C 1-4 alkyl and C 1-4 alkoxy groups, and (b) 0, 1 or 2 —CH 2 -groups are replaced by groups selected from —O—, —S— and —C(O)— groups.

5. A method according to claim 1 , wherein Z represents:

(a) a group of formula -LG, —C(O)-LG, —C(S)-LG or —C(NH)-LG wherein LG is an electrophilic leaving group;

(b) a nucleophile Nu′ selected from —OH, —SH, —NH 2 , —NH(C 1-6 alkyl) and —C(O)NHNH 2 groups;

(c) a cyclic moiety Cyc, which is capable of a ring-opening electrophilic reaction with a nucleophile;

(d) a group of formula —S(O 2 )(Hal), wherein Hal is a halogen atom;

(e) a group of formula —N═C═O or —N═C═S;

(f) a group of formula —S—S(IG′) wherein IG′ represents a group of formula IG;

(g) a group AH, which is a C 6-10 aryl group that is substituted by one or more halogen atoms;

(h) a photoreactive group capable of being activated by exposure to ultraviolet light;

(i) a group of formula —C(O)H or —C(O)(C 1-6 alkyl);

(j) a maleimido group;

(k) a group of formula —C(O)CHCH 2 ;

(l) a group of formula —C(O)C(N 2 )H or -PhN 2 + , where Ph represents a phenyl group;

or

(m) an epoxide group.

6. A method according to claim 5 , wherein:

LG is selected from halogen atoms and —O(IG′), —SH, —S(IG′), —NH 2 , NH(IG′),

N(IG′)(IG″), —N 3 , triflate, tosylate, mesylate, N-hydroxysuccinimidyl, N-hydroxysulfosuccinimidyl, imidazolyl and azide groups, wherein IG′ and IG″ are the same or different and each represents a group of formula IG; and/or

Nu′ is selected from —OH, —SH and —NH 2 groups; and/or

Cyc is selected from the groups

Hal is a chlorine atom; and/or

AH is a phenyl group that is substituted by at least one fluorine atom; and/or

the photoreactive group is selected from:

(a) a C 6-10 aryl group which is substituted by at least one group of formula —N 3 and which is optionally further substituted by one or more halogen atoms;

(b) a benzophenone group;

(c) a group of formula —C(O)C(N 2 )CF 3 ; and

(d) a group of formula -PhC(N 2 )CF 3 , wherein Ph represents a phenyl group.

7. A method according to claim 1 , wherein Z is selected from:

(a) groups of formula -LG, —C(O)-LG and —C(S)-LG, wherein LG is selected from halogen atoms and —O(C 1-6 alkyl), —SH, —S(C 1-6 alkyl), triflate, tosylate, mesylate, N-hydroxysuccinimidyl and N-hydroxysulfosuccinimidyl groups;

(b) groups of formula —OH, —SH and NH 2 ;

(c) group of formula

(d) a maleimide group.

8. A method according to claim 1 , wherein IG represents a moiety which is an unsubstituted C 1-6 alkyl group, C 2-6 alkenyl group or C 2-6 alkynyl group, in which (a) 0 or 1 carbon atom is replaced by a group selected from phenylene, 5- to 6-membered heteroarylene, C 5-6 carbocyclylene and 5- to 6-membered heterocyclylene groups, wherein said phenylene, heteroarylene, carbocyclylene and heterocyclylene groups are unsubstituted or substituted by one or two substituents selected from halogen atoms and C 1 alkyl and C 1-4 alkoxy groups, and (b) 0, 1 or 2 —CH 2 — groups are replaced by groups selected from —O—, —S— and —C(O)— groups.

9. A method according to claim 1 , wherein n is 1.

10. A method according to claim 1 , wherein the compound of formula (Ia) is a compound of formula (Ib)

11. A method according to claim 10 , wherein:

R 33 ′ represents a hydrogen atom or a C 1-6 alkyl group;

Y represents a halogen atom; and

R 2 represents a hydrogen or halogen atom or a C 1-6 alkyl group.

12. A method according to claim 1 , wherein:

F 1 is a peptide or protein comprising at least a first cysteine residue; and

the group F 1 becomes attached to the compound of formula (Ia) via nucleophilic attack of the thiol group of said first cysteine residue at the 2-position of the compound of formula (Ia), such that the group Y is replaced by the thiol group in the first cysteine residue in the group F 1 .

13. A method according to claim 12 , wherein:

R 2 is a group of formula Y;

F 1 further comprises at least a second cysteine residue; and

the group F 1 becomes further attached to the compound of formula (Ia) via nucleophilic attack of the thiol group of said second cysteine residue at the 3-position of the moiety of formula (Ia), such that the group R 2 is replaced by the thiol group in the second cysteine residue in the group F 1 .