Precursors for radiofluorination

Abstract

A method for producing a radiofluorinated compound having an aromatic or heteroaromatic ring carrying [.sup.18F] fluorine as first substituent, a bonding unit, which can bind to a peptide or peptide mimetic, and a spacer group connected via bond A.sup.1 to the bonding unit and via bond A.sup.2 to the ring, wherein the bonding unit has second substituent(s) OH, CONH, and/or COOH. The steps include (a) providing a precursor having the ring carrying a substituent Y, bonding unit with the second substituent(s), and spacer group, wherein substituent Y is N.sup.+(R.sup.1R.sup.2R.sup.3), NO.sub.2, Cl, Br, F, or I, and R.sup.1, R.sup.2, and R.sup.3 are independently C.sub.1-C.sub.6 alkyl; and (b) reacting the precursor with a [.sup.18F] fluoride anion in the presence of an activation salt to the radiofluorinated compound, which has a cation N.sup.+(R.sup.4R.sup.5R.sup.6R.sup.7) with R.sup.4, R.sup.5, R.sup.6, and R.sup.7 being independently C.sub.1-C.sub.6 alkyl, wherein the substituent Y is replaced by [.sup.18F] fluoride.

Claims

1. A precursor for producing a radiofluorinated compound, wherein the precursor has an aromatic or heteroaromatic ring, which carries a substituent Y, a bonding unit, which can bind to a peptide or to a peptide mimetic, and a spacer group, which connects the aromatic or heteroaromatic ring to the bonding unit, wherein the bonding unit carries at least one second substituent selected from the group consisting of OH, CONH, and COOH, wherein the bonding unit is connected to the spacer group via a bond A.sup.1 and the spacer group is connected to the aromatic or heteroaromatic ring via a bond A.sup.2, wherein: the aromatic or heteroaromatic ring, which carries a substituent Y, is of general formula VId ##STR00027## wherein: X each is CR.sup.8 or N, with the provision that at most two of moieties X are N and the remaining of moieties X are CR.sup.8 and R.sup.8 each independently is the bond A.sup.2 to the spacer, hydrogen, or unsubstituted or substituted C.sub.1-C.sub.6 alkyl, with the provision that exactly one residue R.sup.8 is a bond A.sup.2 to the spacer group and the remaining ones of R.sup.8 are the same or different from each other and each represent hydrogen or unsubstituted or substituted C.sub.1-C.sub.6 alkyl; and substituent Y is selected from the group consisting of N.sup.+(R.sup.1R.sup.2R.sup.3), NO.sub.2, Cl, Br, or I, and R.sup.1, R.sup.2, and R.sup.3 are the same or different from each other and each are unsubstituted or substituted C.sub.1-C.sub.6 alkyl; the bonding unit is a bonding unit of general formula I: ##STR00028## wherein A.sup.1 is the bond via which the bonding unit is connected to the spacer group, and m and n are the same or different from each other and each are an integer of from 0 to 10; and the spacer group is a spacer group of general formula II or general formula III: ##STR00029## wherein A.sup.1 is the bond via which the spacer group is connected to the bonding unit, A.sup.2 is the bond via which the spacer group is connected to the aromatic or heteroaromatic ring of the precursor or the radiofluorinated compound, R.sup.9 is hydrogen or an unsubstituted or substituted C.sub.1-C.sub.6 alkyl group, and Z is an unsubstituted or mono- or poly-substituted hydrocarbon.

2. The precursor according to claim 1, wherein Z is a group of formula VII: ##STR00030##

3. A precursor for producing a radiofluorinated compound, wherein the precursor is a compound of formula IVa: ##STR00031## wherein R.sup.1, R.sup.2, and R.sup.3 are the same or different from each other and each are unsubstituted or substituted C.sub.1-C.sub.6 alkyl.

4. A precursor for producing a radiofluorinated compound, wherein the precursor is a compound of formula Va: ##STR00032## wherein R.sup.1, R.sup.2, and R.sup.3 are the same or different from each other and each are unsubstituted or substituted C.sub.1-C.sub.6 alkyl.

Description

DETAILED DESCRIPTION

(1) The term C.sub.1-C.sub.6 alkyl relates to straight or branched, saturated, aliphatic hydrocarbon groups with 1 to 6 carbon atoms. Examples of C.sub.1-C.sub.6 alkyl groups are methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl.

(2) The term substituted C.sub.1-C.sub.6 alkyl relates to C.sub.1-C.sub.6 alkyl, as defined above, which has one or more substituents selected from the group consisting of NH.sub.2, NH(C.sub.1-C.sub.4 alkyl), N(C.sub.1-C.sub.4 alkyl).sub.2, halogen, C.sub.1-C.sub.4 alkyl, OH, O(C.sub.1-C.sub.4 alkyl), NO.sub.2, CN, CO.sub.2H or CO.sub.2(C.sub.1-C.sub.4 alkyl), wherein each of the preceding C.sub.1-C.sub.4 alkyl groups is unsubstituted or substituted with at least one halogen atom. The term halogen relates to fluorine, chlorine, bromine, and iodine.

(3) In the present invention, the term precursor relates to a chemical compound that can be converted to a radiochemical compound, i.e. the radiofluorinated compound, by radiofluorination without using protective groups. The precursor has no carboxylate groups, in particular no carboxylate anions COO.sup.. Thus, the precursor also has no carboxylate groups in the form of a salt with a cation, for example a cationic chelate or a quaternary ammonium cation.

(4) However, the precursor can have one or more carboxyl groups COOH. With the method according to the invention a precursor, which has one or more carboxyl groups, can be converted to a radiofluorinated compound without using protective groups. The precursor only differs from the radiofluorinated compound in that the substituent Y is replaced by [.sup.18F] fluorine. Substituent Y of the precursor and the [.sup.18F] fluorine substituent of the radiofluorinated compound are in the same position.

(5) Preferably, substituent Y is N.sup.+(R.sup.1R.sup.2R.sup.3), wherein R.sup.1, R.sup.2, and R.sup.3 are the same or different from each other and each are unsubstituted or substituted C.sub.1-C.sub.6 alkyl. Preferably, R.sup.1, R.sup.2, and R.sup.3 are the same and are methyl or butyl, wherein methyl is particularly preferred. In this case, the group N.sup.+(R.sup.1R.sup.2R.sup.3), which carries the aromatic or heteroaromatic ring of the precursor, is a quaternary trimethylammonium group. The anion relating to the group N.sup.+(R.sup.1R.sup.2R.sup.3) of the precursor can be any anion. For example, the anion can be selected from the group comprising a fluorine, iodine, bromine, chlorine, sulphonate, sulphate, phosphate, alkylsulphate, arylsulphate, or carboxylate anion. Preferably, as the anion a carboxylate anion can be provided, for example CF.sub.3COO.sup., CH.sub.3COO.sup., C.sub.2H.sub.5COO.sup., or HCOO.sup..

(6) If R.sup.1, R.sup.2, and R.sup.3 in the group N.sup.+(R.sup.1R.sup.2R.sup.3) each are methyl, then it is preferred that the anion of the group N.sup.+(R.sup.1R.sup.2R.sup.3) is selected from the group consisting of trifluoroacetate (CF.sub.3COO.sup.), acetate (CH.sub.3COO.sup.), propionate (C.sub.2H.sub.5COO.sup.), or formate (HCOO.sup.).

(7) The aromatic or heteroaromatic ring of the precursor and thus, of the radiochemical compound, is preferably a monocyclic ring or a fused ring system of two or more rings with a monocyclic ring being preferred. The heteroatom of a heteroaromatic ring is preferably selected from the group comprising N, O, and S. Preferably, the heteroatom is N. A heteroaromatic ring can have one or more heteroatoms. Preferably, the heteroaromatic ring has one or two heteroatoms, preferably one or two nitrogen atoms. In this case, the ring can be a pyridine ring, a pyridazine ring, a pyrimidine ring, or a pyrazine ring.

(8) A preferred aromatic or heteroaromatic ring, which carries a substituent Y, is shown in the general formula VI:

(9) ##STR00004##
wherein X is CR.sup.8 or N, Y is N.sup.+(R.sup.1R.sup.2R.sup.3), NO.sub.2, Cl, Br, F, or I, wherein R.sup.1, R.sup.2, and R.sup.3 are defined as above and R.sup.8 each independently is the bond A.sup.2 to the spacer, hydrogen or unsubstituted or substituted C.sub.1-C.sub.6 alkyl, with the provision that exactly one residue R.sup.8 is a bond A.sup.2 to the spacer group and the remaining one of R.sup.8 are the same or different from each other and each represent hydrogen or unsubstituted or substituted C.sub.1-C.sub.6 alkyl.

(10) A particularly preferred aromatic or heteroaromatic ring has the group N.sup.+(R.sup.1R.sup.2R.sup.3) as substituent Y and bond A.sup.2 in para position to the group N.sup.+(R.sup.1R.sup.2R.sup.3), as is shown in general formula VIa:

(11) ##STR00005##
wherein X is CR.sup.8 or N, R.sup.1, R.sup.2, and R.sup.3 are defined as above and R.sup.8 each independently is hydrogen or unsubstituted or substituted C.sub.1-C.sub.6 alkyl.

(12) A more preferred aromatic or heteroaromatic ring, which carries a group N.sup.+(R.sup.1R.sup.2R.sup.3) as substituent Y, has bond A.sup.2 in para position to group N.sup.+(R.sup.1R.sup.2R.sup.3), as is shown in general formula VIb:

(13) ##STR00006##
wherein X is CR.sup.8 or N, R.sup.1, R.sup.2, and R.sup.3 are defined as above and R.sup.8 is hydrogen or unsubstituted or substituted C.sub.1-C.sub.6 alkyl. Preferably, X is N and R.sup.1, R.sup.2, and R.sup.3 are defined as above.

(14) A particularly preferred embodiment of the aromatic or heteroaromatic ring, which carries a group N.sup.+(R.sup.1R.sup.2R.sup.3) as substituent Y, is shown in formula VIc:

(15) ##STR00007##
wherein Me represents methyl. In formula VIc, with respect to general formula VI, X is N; R.sup.1, R.sup.2, and R.sup.3 are methyl; R.sup.8 in para position to the N.sup.+(R.sup.1R.sup.2R.sup.3) group is A.sup.2, and the remaining R.sup.8 are hydrogen.

(16) A preferred aromatic or heteroaromatic ring, which carries a substituent Y, is shown in general formula VId:

(17) ##STR00008##
wherein X each is CR.sup.8 or N, with the provision that at most two of the moieties X are N and the remaining ones of moieties X are CR.sup.8; and Y is N.sup.+(R.sup.1R.sup.2R.sup.3), NO.sub.2, Cl, Br, F, or I, wherein R.sup.1, R.sup.2, and R.sup.3 are as defined above and R.sup.8 each independently is the bond A.sup.2 to the spacer, hydrogen or unsubstituted or substituted C.sub.1-C.sub.6 alkyl, with the provision that exactly one of residues R.sup.8 is a bond A.sup.2 to the spacer group and the remaining ones of R.sup.8 are the same or different from each other and each represent hydrogen or unsubstituted or substituted C.sub.1-C.sub.6 alkyl.

(18) The bonding unit is able to bind to a peptide or to a peptide mimetic. For example, the radiochemical compound can specifically couple to a functional unit of the peptide or the peptide mimetic via the bonding unit. The bonding unit of the precursor and thus, the radiochemical compound may be a bonding unit of general formula I:

(19) ##STR00009##
wherein A.sup.1 is the bond via which the bonding unit is connected to the spacer group, and m and n are the same or different from each other and each are an integer of from 0 to 10. Thus, m and n each independently may be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. Preferably, m=1 and n=1. The bonding unit shown in formula I is able to bind to the protein PSMA (prostate-specific membrane antigen). PSMA is a protein that is expressed in the prostate of a mammal. With prostatic cancer it is expressed to a higher extent compared to a healthy prostate.

(20) The spacer group of the precursor and thus, the radiochemical compound is preferably a spacer group of general formula II or general formula III.

(21) ##STR00010##
wherein A.sup.1 is the bond via which the spacer group is connected to the bonding unit, A.sup.2 is the bond via which the spacer group is connected to the aromatic or heteroaromatic ring of the precursor or the radiochemical compound, R.sup.9 is hydrogen or an unsubstituted or substituted C.sub.1-C.sub.6 alkyl group, and Z is an unsubstituted or mono- or poly-substituted hydrocarbon. Preferably, R.sup.9 is hydrogen.

(22) In one embodiment of the invention Z is a group of formula VII:

(23) ##STR00011##

(24) A spacer group of formula III the Z group of which has the meaning shown in formula VII is in formula IIIa:

(25) ##STR00012##
wherein R.sup.9 is as defined above. Preferably, R.sup.9 is hydrogen.

(26) According to the invention, reacting the precursor is to be done with a [.sup.18F] fluoride anion in the presence of an activation salt to the radiofluorinated compound. Here, the substituent Y is replaced [.sup.18F] fluoride. The activation salt is for activation of the [.sup.18F] fluoride anion. The activation salt has a cation with the general formula N.sup.+(R.sup.4R.sup.5R.sup.6R.sup.7), wherein R.sup.4, R.sup.5, R.sup.6, and R.sup.7 are the same or different from each other and each are unsubstituted or substituted C.sub.1-C.sub.6 alkyl. It has been shown that such activation salts are suitable not only to react the described precursors to radiofluorinated compounds, but also for radiofluorination of other precursors. Preferably, R.sup.4, R.sup.5, R.sup.6, and R.sup.7 each are unsubstituted C.sub.1-C.sub.6 alkyl, more preferred propyl, butyl, or pentyl, especially preferred n-butyl each. Preferably, the activation salt has an anion selected from the group comprising hydrogen carbonate (HCO.sub.3.sup.), hydrogen sulphate (HSO.sub.4.sup.), oxalate, phosphate, and toluenesulphonate. Hydrogen carbonate and phosphate are more preferred. Phosphate is particularly preferred. The cation of general formula N.sup.+(R.sup.4R.sup.5R.sup.6R.sup.7) and the anion are present in the activation salt in a stoichiometric ratio. In a preferred embodiment, the activation salt is tetra-n-butyl-ammonium hydrogen carbonate or tetra-n-butyl-ammonium phosphate, wherein tetra-n-butyl-ammonium phosphate is particularly preferred. In the following, an activation salt having the tetra-n-butyl-ammonium cation is also referred to as TBA.

(27) Using an activation salt having a cation of general formula N.sup.+(R.sup.4R.sup.5R.sup.6R.sup.7), wherein R.sup.4, R.sup.5, R.sup.6, and R.sup.7 are the same or different from each other and each are unsubstituted or substituted C.sub.1-C.sub.6 alkyl, and hydrogen sulphate, oxalate, phosphate, and toluenesulphonate as the anion, to activate [.sup.18F] fluoride anions is unknown so far. These activation salts are not limited to the reaction of the described precursors to radiofluorinated compounds, but can also be used for radiofluorination of other precursors. Preferably, R.sup.4, R.sup.5, R.sup.6, and R.sup.7 in the hydrogen sulphate, oxalate, phosphate, and toluenesulphonate salt each are unsubstituted C.sub.1-C.sub.6 alkyl, more preferred propyl, butyl, or pentyl, particularly preferred n-butyl each. Hydrogen carbonate and phosphate salts are more preferred. Phosphate salt is particularly preferred. In a preferred embodiment the activation salt is tetra-n-butyl-ammonium hydrogen carbonate or tetra-n-butyl-ammonium phosphate, wherein tetra-n-butyl-ammonium phosphate is particularly preferred.

(28) Preferably, the activation salt is in a polar solution, particularly preferred in a solution with water or a hydrous mixed solvent. The mixed solvent may be for example water containing an alcohol such as ethanol. The alcoholic additive is to stabilize the solution. The activation salt may be provided as a 0.001 to 0.1 M solution, in particular as a 0.075 M solution, for example.

(29) The radiofluorinated compound is for example [.sup.18F]-DCFPyL (see Formula 1, supra) or [.sup.18F]F-PSMA-1007 (see formula 2, supra). A precursor that is preferred for the preparation of [.sup.18F]-DCFPyL is a compound of general formula IV:

(30) ##STR00013##
wherein substituent Y is selected from the group consisting of N.sup.+(R.sup.1R.sup.2R.sup.3), NO.sub.2, Cl, Br, F, or I, and R.sup.1, R.sup.2, and R.sup.3 are the same or different from each other and each are unsubstituted or substituted C.sub.1-C.sub.6 alkyl. The bonding unit of the precursor shown in formula IV corresponds to the bonding unit shown in formula I, wherein m and n each are 1.

(31) A precursor that is more preferred for the preparation of [.sup.18F]-DCFPyL is a compound of general formula IVa:

(32) ##STR00014##
wherein R.sup.1, R.sup.2, and R.sup.3 are the same or different from each other and each are unsubstituted or substituted C.sub.1-C.sub.6 alkyl. Particularly preferred R.sup.1, R.sup.2, and R.sup.3 each are methyl. A precursor of formula IVa, in which R.sup.1, R.sup.2, and R.sup.3 each are methyl, is illustrated in formula IVb.

(33) ##STR00015##

(34) A precursor preferred for the preparation of [.sup.18F]F-PSMA-1007 is a compound of general formula V:

(35) ##STR00016##
wherein substituent Y is selected from the group consisting of N.sup.+(R.sup.1R.sup.2R.sup.3), NO.sub.2, Cl, Br, F, or I, and R.sup.1, R.sup.2, and R.sup.3 are the same or different from each other and each are unsubstituted or substituted C.sub.1-C.sub.6 alkyl. The bonding unit of the precursor shown in formula V corresponds to the bonding unit shown in formula I, wherein m and n each are 1.

(36) A precursor that is more preferred for the preparation of [.sup.18F]F-PSMA-1007 is a compound of general formula Va:

(37) ##STR00017##
wherein R.sup.1, R.sup.2, and R.sup.3 are the same or different from each other and each are unsubstituted or substituted C.sub.1-C.sub.6 alkyl. Particularly preferred, R.sup.1, R.sup.2, and R.sup.3 each are methyl. A precursor of formula Va, in which R.sup.1, R.sup.2, and R.sup.3 each are methyl, is illustrated in formula Vb.

(38) ##STR00018##

(39) Preferably, the precursor is provided in a aprotic, polar solvent such as acetonitrile, dimethylformamide (DMF), N,N-dimethylacetamide (DMAA), N-methyl-2-pyrrolidone (NMP), dimethylsulfoxide (DMSO) or mixtures thereof.

(40) The [.sup.18F] fluoride anion used in step (b) can be prepared by means of known methods. For example, the [.sup.18F] fluoride anion is prepared in the cyclotron by irradiating H.sub.2.sup.18O enriched to at least 97% with protons of an energy of 9.6 MeV. The so obtained aqueous [.sup.18F] fluoride solution is fixed on an anion exchange cartridge (QMA) and transferred into a reaction vessel by means of a phase transfer catalyst (PTC), such as crown ethers, quaternary ammonium salts, or alkali or alkaline-earth salts. As the PTC it is preferably made use of a [2,2,2]-cryptand (Kryptofix or K222), tetra-n-butyl-ammonium phosphate, hydroxide, oxalate, toluenesulphonate, or optionally other crown ethers, such as 18-crown-6. After an azeotropic dehydration the precursor is dissolved in an organic solvent and added to the dried reaction mixture. The organic solvent may be an aprotic, polar solvent such as acetonitrile, dimethylformamide (DMF), N,N-dimethylacetamide (DMAA), N-methyl-2-pyrrolidone (NMP), dimethylsulfoxide (DMSO), or mixtures thereof. Preferably, dimethylsulfoxide is used as the solvent.

(41) Step (b) is preferably carried out under a thermal reaction regime in the closed reaction vessel at an elevated temperature. Step (b) of the method according to the invention is preferably carried out in an aprotic, polar solvent, such as acetonitrile, dimethylformamide (DMF), dimethylsulfoxide (DMSO), or mixtures thereof. Preferably, dimethylsulfoxide is used as the solvent. Preferably, the method is carried out at a pH value of 1 to 8. Preferably, the pH value is in the range of 4 to 8, particularly preferred at 5. However, the method can also be carried out at a pH value above 8, where however lower yields are achieved. The inventors have surprisingly found that just at a pH value in the range of from 4 to 8 less by-compounds are generated and an extremely high labeling yield can be achieved.

(42) Step (b) of the method according to the invention is preferably carried out for a time period of from 1 to 60 min, more preferably from 3 to 30 min, and particularly preferred from 8 to 20 min.

(43) Step (b) of the method according to the invention is preferably carried out at temperatures below 100 C., more preferably at temperatures between room temperature and 95 C., even more preferably between room temperature and 90 C., and particularly preferred at temperatures between 70 and 90 C.

(44) Step (b) of the method according to the invention may also be carried out as a microwave-assisted reaction. For that, microwaves of a wattage of 50 to 150 W, preferably 75 to 85 W are radiated onto a specific closed reaction vessel.

(45) To determine the labeling yield and radioactive by-products thin-layer chromatography (TLC) and high performance liquid chromatography (HPLC) can be used.

(46) Scheme 3 illustrates a preferred embodiment of the method according to the invention. Here, a precursor of formula IV is reacted to [.sup.18F]-DCFPyL in the presence of [.sup.18F] fluoride anions and an activation salt:

(47) ##STR00019##

(48) It should be noted that the precursor can have another anion instead of the CF.sub.3COO.sup. anion. Preferably, the activation salt is TBA, particularly preferred TBA phosphate.

(49) Scheme 3a illustrates a preferred embodiment of the method according to the invention. Here, a precursor of formula IVa is reacted to [.sup.18F]-DCFPyL in the presence of [.sup.18F] fluoride anions and an activation salt:

(50) ##STR00020##

(51) It should be noted that the precursor can have another anion instead of the CF.sub.3COO.sup. anion. Preferably, the activation salt is TBA, particularly preferred TBA phosphate.

(52) In a preferred embodiment a precursor of formula IVb for the preparation of [.sup.18F]-DCFPyL in the presence of [.sup.18F] fluorine anions and TBA, preferably TBA phosphate, as an activation salt is reacted, as is shown in scheme 3b.

(53) ##STR00021##

(54) It should be noted that the precursor can have another anion instead of the CF.sub.3COO.sup. anion.

(55) Scheme 4 illustrates a preferred embodiment of the method according to the invention. Here, a precursor of formula V is reacted to [.sup.18F]F-PSMA-1007 in the presence of [.sup.18F] fluoride aninnc and an activation

(56) ##STR00022##

(57) It should be noted that the precursor can have another anion instead of the CF.sub.3COO.sup. anion. Preferably, the activation salt is TBA, particularly preferred TBA phosphate.

(58) Scheme 4a illustrates a preferred embodiment of the method according to the invention. Here, a precursor of formula Va is reacted to [.sup.18F]F-PSMA-1007 in the presence of [.sup.18F] fluoride anions and an activation salt:

(59) ##STR00023##

(60) It should be noted that the precursor can have another anion instead of the CF.sub.3COO.sup. anion. Preferably, the activation salt is TBA, particularly preferred TBA phosphate.

(61) In a particularly preferred embodiment a precursor of formula Vb for the preparation of [.sup.18F]F-PSMA-1007 in the presence of [.sup.18F] fluorine anions and TBA, preferably TBA phosnhate, as an activation salt is reacted, as is shown in scheme 4b.

(62) ##STR00024##

(63) It should be noted that the precursor can have another anion instead of the CF.sub.3COO.sup. anion.

(64) According to the invention, further a precursor for the preparation of a radiofluorinated compound is provided. The precursor has an aromatic or heteroaromatic ring, which carries a substituent Y, a bonding unit, which can bind to a peptide or peptide mimetic, as well as a spacer group, which connects the aromatic or heteroaromatic ring to the bonding unit. The bonding unit carries at least one second substituent selected from the group consisting of OH, CONH, and COOH, wherein the bonding unit is connected to the spacer group via a bond A.sup.1 and the spacer group is connected to the aromatic or heteroaromatic ring via a bond A.sup.2. Here, substituent Y is selected from the group consisting of N.sup.+(R.sup.1R.sup.2R.sup.3), NO.sub.2, Cl, Br, F, or I, R.sup.1, R.sup.2, and R.sup.3 are the same or different from each other and each are unsubstituted or substituted C.sub.1-C.sub.6 alkyl. Further details on the precursor according to the invention have been described above in context with the method according to the invention.

(65) According to the invention, further there is provided the use of the precursor according to the invention for the preparation of a radiofluorinated compound, which has an aromatic or heteroaromatic ring, which carries the [.sup.18F] fluorine as the first substituent, a bonding unit, which can bind to a peptide or a peptide mimetic, as well as a spacer group, which connects the aromatic or heteroaromatic ring to the bonding unit. The bonding unit can carry at least one second substituent selected from the group consisting of OH, CONH, and COOH, wherein the bonding unit is connected to the spacer group via a bond A.sup.1 and the spacer group is connected to the aromatic or heteroaromatic ring via a bond A.sup.2.

(66) The invention allows a one-stage synthesis of the shown radiofluorinated compounds. On the one hand, this shortens the synthesis time. On the other hand, the labeling yields achieved can be more than twice as high as with the two-stage process known in the literature. Moreover, the reaction product of a one-stage synthesis is easier to purify, by which it can be refrained from HPLC that is costly in terms of equipment. The radiofluorinated compounds can be purified very easily and less time-consuming with cartridges, so-called SPE cartridges. Further, it is preferred to avoid concentrated acids and bases in the GMP environment (GMP=good manufacturing practice), since in GMP fields often corrodible stainless steel has been used. The simplicity of the method according to the invention allows an automated synthesis of the radiofluorinated compound according to the invention, for example by means of a disposable cassette and a reagent kit on a common synthesis module. Purification can be carried out during the synthesis by means of the SPE cartridge, so that at the end of the synthesis a ready-to-use solution of the radiofluorinated compound according to the invention can be provided.

(67) The precursor according to the invention carries the at least one second substituent, i.e. at least one unprotected OH, CONH and/or COOH group, which is also carried by the target compound, i.e. the radiofluorinated compound. It was not to be expected that radioactive labelings at compounds carrying unprotected OH, CONH, and COOH groups do work. With the present invention in practice a significant simplification of the automated synthesis and thus, the preparation of the radiofluorinated compound can be achieved, since the synthesis in at least two stages, as before, is no longer needed, but can be done in one stage with significant time saving. Time saving allows a significantly increased yield and thus, an easier and higher availability of the radiofluorinated compound. Therefore, more activity is gained from a radiosynthesis, and thus, when using the radiofluorinated compound prepared in the radiosynthesis as a radiotracer, more patients can be examined.

(68) The invention is explained in detail with the help of examples that are not intended to limit the invention.

Example 1

(69) Synthesis of a Precursor of Formula IVb

(70) ##STR00025##

(71) Synthesis of the starting compound VI is as described in literature (Ravert et al., J. Label Compd. Radiopharm 2016, 59, 439-50; Bouvet et al., EJNMMMI Research, 2016, 6: 40). In a mixture of 23.5 ml of trifluoroacetic acid, 0.62 ml of triisopropylsilane, and 0.62 ml of water 2.48 g of the starting compound XX were dissolved and stirred for 3 h at room temperature. Subsequently, the reaction mixture was dropwise added to 241 ml of MTB ether under cooling with an ice bath and vigorously stirring. The precipitated white solid was sucked off by a frit and washed two times with 100 ml of MTB ether. 1.82 g (84%) of the precursor of formula IVb (=5-((S)-5-carboxy-5-(3-((S)-1,3-dicarboxy-propyl)ureido)pentyl-carbamoyl)-N,N,N-trimethylpyridine-2-aminium-2,2,2-trifluoro-acetate) were separated as a white solid.

Example 2

(72) Synthesis of a Precursor of Formula Vb

(73) ##STR00026##

(74) The synthesis of the starting compound VIII is as described in literature (Cardinale et al., J. Nucl. Med. 2016, accepted for publication; WO 2016/062370 A1). 0.2 mmol of the starting compound VIII were shaken in 3.5 ml of dimethylformamide for 30 min. Thereafter, 109 mg of N,N,N-trimethyl-5-((2,3,5,6-tetrafluorophenoxy)-carbonyl)pyridine-2-aminiumchloride (Olberg et al., J. Med. Chem. 2010, 53, 1732-1740) and 0.042 ml of triethylamine were added. The reaction mixture was shaken for 2 h, before the resin was filtered and washed three times with DMF and three times with dichloromethane. For cleavage and deprotection, the resin was shaken with a mixture of 4 ml of trifluoroacetic acid, 0.11 ml of triisopropylsilane, and 0.11 ml of water for 90 min. Subsequently, the mixture was filtered, and the filtrate was added dropwise to 40 ml of MTB ether. The mixture was centrifuged, the supernatant solution was pipetted off, and the residue was washed three times with MTB ether. Purification was by HPLC. 172 mg (72%) of the precursor of formula Vb (=5-(S)-4-carboxy-1-(S)-4-carboxy-1-(4-(S)-1-((S)-5-carboxy-5-(3-((S)-1,3-dicarboxy-propyl)-ureido)pentylamino)-3-(naphthalene-2-yl)-1-oxopropane-2-ylcarbamoyl)-benzylamino)-1-oxobutane-2-ylamino)-1-oxobutane-2-ylcarbamoyl)-N,N,N-trimethylpyridine-2-aminium-2,2,2-trifluoroacetate) were separated as a white solid.

Example 3

(75) Reaction of a Precursor of Formula IVb in the Presence of Tetra-N-Butyl-Ammonium-Hydrogen Carbonate to [.sup.18F]-DCFPyL

(76) A reaction mixture of 7.5 mg of a precursor of formula IVb in 1 ml of DMF, 1 ml of 0.075M tetra-n-butyl-ammonium hydrogen carbonate (TBA-HCO.sub.3) and [.sup.18F] fluoride anions was reacted at a pH value of about 8.5 for 14 min at 75 C. 47.9% of [.sup.18F]-DCFPyL were obtained. Additionally, radioactive by-compounds could be detected. The proportion of [.sup.18F] fluoride was 28.6%.

Example 4

(77) Reaction of a Precursor of Formula IVb in the Presence of Tetra-N-Butyl-Ammonium Toluene Sulphonate to [.sup.18F]-DCFPyL

(78) A reaction mixture of 7.5 mg of a precursor of formula IVb in 1 ml of DMF, 750 l of 0.075M tetra-n-butyl-ammonium toluene sulphonate (TBA toluene sulphonate), and [.sup.18F] fluoride anions was reacted at a pH value of about 5.0 for 14 min at 75 C. 37.4% of [.sup.18F]-DCFPyL and 30.9% of [.sup.18F] fluoride were detected. Additionally, radioactive by-compounds were detected the proportion of which was approx. 30%.

Example 5

(79) Reaction of a Precursor of Formula IVb in the Presence of Tetra-N-Butyl-Ammonium Phosphate to [.sup.18F]-DCFPyL

(80) A reaction mixture of 2.5 mg of a precursor of formula IVb in 1.5 ml of DMF, 750 l of 0.075M tetra-n-butyl-ammonium phosphate (TBA phosphate) and [.sup.18F] fluoride anions was reacted at a pH value of about 4.7 for 10 min at 85 C. Under these conditions, the precursor was almost quantitatively converted to [.sup.18F]-DCFPyL (97.0%). The by-compounds could be reduced to less than 2%, residual [.sup.18F] fluoride could only be detected in traces.

Example 6

(81) Reaction of a Precursor of Formula IVb in the Presence of Tetra-N-Butyl-Ammonium Hydrogen Sulphate to [.sup.18F]-DCFPyL

(82) A reaction mixture of 7.5 mg of a precursor of formula IVb in 1 ml of DMF, 750 l of 0.075M tetra-n-butyl-ammonium hydrogen sulphate (TBA hydrogen sulphate) and [.sup.18F] fluoride anions was reacted at a pH value of about 1.7 for 14 min at 75 C. 15.6% of [.sup.18F]-DCFPyL were obtained, whereas the proportion of [.sup.18F] fluoride was 73.4%. Thus, labeling with [.sup.18F] fluoride anions was relatively poor.

(83) Examples 3 to 6 show that the reaction of precursors of formula IVb with [.sup.18F] fluoride anions in the presence of TBA as an activation salt in a one-stage method results in relatively high yields of the radiofluorinated compound [.sup.18F]-DCFPyL. Example 5 shows that in the slightly acidic pH range with TBA phosphate only traces of the by-compounds are generated and an extremely high labeling yield can be achieved.

Example 7

(84) Reaction of a Precursor of Formula Vb in the Presence of Tetra-N-Butyl-Ammonium Hydrogen Carbonate to [.sup.18F]-PSMA-1007

(85) A reaction mixture of 10 mg of a precursor of formula Vb in a mixture of 1 ml of acetonitrile and 600 l of DMF, 750 l of 0.075M TBA hydrogen carbonate, and [.sup.18F] fluoride anions was incubated at a pH value of approx. 7 for 10 min at 120 C. In addition to 37.9% of free [.sup.18F] fluoride, 59.3% of [.sup.18F]-PSMA-1007 were detected. A radioactive by-product could be detected in traces.

Example 8

(86) Reaction of a Precursor of Formula Vb in the Presence of Tetra-N-Butyl-Ammonium Hydrogen carbonate to [.sup.18F]-PSMA-1007

(87) A reaction mixture of 2.5 mg of a precursor of formula Vb in 1.5 ml of DMF, 750 l of 0.075M TBA hydrogen carbonate, and [.sup.18F] fluoride anions was incubated at a pH value of approx. 7 for 10 min at 85 C. In addition to 8.2% of free [.sup.18F] fluoride, 90.7% of [.sup.18F]-PSMA-1007 were detected. A radioactive by-product could be detected in traces.

Example 9

(88) Reaction of a Precursor of Formula Vb in the Presence of Tetra-N-Butyl-Ammonium Phosphate to [.sup.18F]-PSMA-1007

(89) A reaction mixture of 2.5 mg of a precursor of formula Vb in 1.5 ml of DMF, 750 l of 0.075M TBA phosphate, and [.sup.18F] fluoride anions was incubated at a pH value of approx. 4.7 for 10 min at 85 C. The desired product [.sup.18F]-PSMA-1007 was quantitatively formed (99.6%). Free [.sup.18F] fluoride could only be detected in traces.

(90) Examples 7 to 9 show that the reaction of precursors of formula Vb with [.sup.18F] fluoride anions in the presence of TBA as an activation salt in a one-stage method results in relatively high yields of the radiofluorinated compound [.sup.18F]-PSMA-1007. Example 9 shows that in the slightly acidic pH range with TBA phosphate a quantitative labeling yield can be achieved.

Example 10

(91) Fully Automated Reaction of a Precursor of Formula Vb in the Presence of Tetra-N-Butyl-Ammonium Hydrogen Carbonate to [.sup.18F]-PSMA-1007 by Means of a Synthesis Module GE TRACERlab MX.sub.FDG

(92) With solvent-resistant stopcocks a cassette for the synthesis of [.sup.18F]-PSMA-1007 was established in analogy to a FDG synthesis cassette on a GE TRACERlab MX.sub.FDG and a synthesis sequence was developed. In detail, the synthesis proceeds in accordance with the following steps: concentrating the [.sup.18F] fluoride on a QMA cartridge, elution with 0.750 ml of TBA hydrogen carbonate, and subsequently drying at 95 C. for 15 min, radioactive labeling with 3 mg of a precursor of formula Vb in 2 ml of DMF for 14 min at 85 C., SPE purification and reformulation. [.sup.18F]-PSMA-1007 could be obtained in radiochemical yields >40%. The radiochemical purity was >95%.