INTERMEDIATES FOR CHELATING AGENTS WITH PREFIXED SYMMETRY AND PROCESS FOR THEIR PREPARATION

Abstract: The preparation of compounds of formula (I), wherein R and R1 have the meanings specified in claim 1, is disclosed; compounds (I) are useful intermediates for the preparation of chelating agents.

Description: INTERMEDIATES FOR CHELATING AGENTS WITH PREFIXED SYMMETRY AND PROCESS FOR THEIR PREPARATION The present invention relates to 1,7-disubstituted 1,4 ,7,10-tetraazacyclododecanes which are useful intermediates for chelating agents and to a process for the preparation thereof. The chemistry of polyazamacrocycles with coordinating side arms, which increase the ligating ability of the acrocycles, has developed quickly over the last decade (P.V. Bernhardt and G.A. Lawrance, Coord. Chem. Rev., 1990, 104,297). Derivatives of 1,4, 7,10-tetraazacyclododecane (TAZA) which contain additional donor groups, have been widely investigated due to the applications found for some of their metal complexes. Relevant examples are given by the use of the Gd complex of 1,4,7,10-tetraazacyclododecane- tetraacetic acid (DOTA) as a contrast agent for in vivo magnetic resonance imaging (M. Magerstaedt, O.A. Gansow, M.W. Brechbiel, D. Colcher, L. Baltzer, R.H. Knop, M.E. Girton Naegele and M. , Magn. Reson. Med. , 1986, 3, 808) and of 90 Y co plexed DOTA derivatives attached to monoclonal antibodies in radioimmunotherapy (D. Parker, Chem. Soc. Rev., 1990, 19, 271; S.V. Deshpande, S.J. De Nardo, D.L. Kukis, M. . Moi, M.J. MσCall, G.L. De Nardo and C.F. Meares, J. Nucl. Med., 1990, 31, 473). Well known are derivatives of TAZA bearing four identical residues on the nitrogen atoms. On the contrary, TAZA derivatives containing different , coordinating side arms on the nitrogen atoms have received little attention, likely due to the difficulties involved in their synthesis. In this con¬ text, 1,7-disubstituted-l,4,7,10-tetraazacyclododecanes can be very useful in order to obtain chelating agents with prefixed symmetry. These compounds can, in principle, be synthesized (T.A. Kaden, Top. Curr. Chem., 1984, 121, 154) by classical condensation according to Richman and Atkins (J.E. Rich an and T.J. Atkins, J. Am. Chem. Soc, 1974, 96, 2268; T.J. Atkins, J. E. Richman and .F. Oettle, Org. Synth., 58, 86). However, the nature of the residues, which can be introduced into positions 1 and 7 by this synthetic approach, is severely limited by the harsh conditions required, in particularly during the deprotecting steps. A preferred embodiment of this invention relates to these compounds useful for the selective preparation of chelating agents with prefixed symmetry, said compounds consisting in 1,7-disubstituted derivatives of 1, ,7,10-tetraazacyclodecane of general formula (I) wherein R is a formyl group or a derivative thereof, ^ is: a) a straight or branched alkyl group C*t-C 2Q , which is substituted or not by groups able to bind to proteins (for example OH, NH,, COOH, CHO, SH and so on) or by their precursors (for example 0 2 , NO, CN, COOR and so on),b) an arylalkyl group C--_c 19 which is substituted or not on the aryl rest by one or more C,- C 4 alkyl, C 1 -C 4 alcoxy or halogen groups or by groups able to bind to proteins (for example OH, NH-, COOH, CHO, SH and so on) or by their precursors (for example N0 2 , NO, CN, COOR and so on) , c) a group alkoxy(C 1 - C 4 )carbonylmethyl or 2-[alkoxy(C 1 -C 4 )carbonyl]ethyl, d) a group of formula: -(CH 2 ) n _R 2 wherein n = 1-4 and R 2 is a free or protected formyl group (for example an acetal group) or a precusor thereof. The coumpounds of formula I are meant for the preparation of chelants with prefixed symmetry derived from 1,4,7,10-tetraazacyclododecane, by substituting the hydrogen atoms in 4 and 10 positions with specific functional groups, if necessary after converting the formyl group in 1- and/or the substituents in 7- position of the macrocycle into other suitable groups. Non-limitating examples of compounds of formula (I) are the ones wherein χ is alkyl Cg-C 18 , benzyl, triphenylmethyl, t-butoxycarbonylmethyl, or a group of formula - (CH 2^n -:R 2 wherein n = 1 or 2 and 2 is a group -CH(OCH 3 ) 2 , -CH(OC 2 H 5 ) 2 or 1,3-dioxol-2-yl. Another preferred embodiment of the invention relates to a process for the preparation of compounds of formula (I), according to the reaction scheme underneath given: Alcohol/H,0 (I) in vhich R - CHO According to this scheme, the mono-substituted compounds of formula (II) (where R, has the meanings given above) are converted, by reaction with dialkylacetals of N,N-dialkylformamide of formula (III) (where ^ and R 4 , equal or different between them, are alkyl groups C- L -c 4 , preferably ethyl or methyl), into the corresponding derivates of formula (IV) and these ones are then submitted to hydrolysis. The preparation of -substituted 1,4,7,10- tetraazacyclododecanes of formula (II) occurs by reacting a compound of formula R,-χ (where X is a leaving group, preferably halogen such as chlorine or bromine) with an excess of 1,4,7,10-te- traazacyclododecane, in an inert solvent, for example acetonitrile. The molar ratio between R-.-X and tetraazacyclododecane ranges from 1:5 to 1:15, and pre¬ ferably is 1:10. The condensation is preferably carried out at the refluxing temperature of the solvent. When the reaction ends, the cooling of the mixture causes the precipitation of the tetraazacyclododecane in excess, which is recovered. After elimination of the solvent, the desired compound is purified by crystallization or chromatography. The conversion of the R- j^ -substituted 1,4,7,10- tetraazacyclododecanes of formula (II) into the corresponding derivatives of formula (IV) can be made according to the procedure disclosed in the European patent EP 292689 (M.F. Tweedle et al. , 1988) in which 1,4,7,10-tetraazacyclododecane is reacted with a N,N- dialkylformamide-dialkylacetal (III) (preferably the dimethyl- or diethylacetal of dimethylformamide) in solvents like aromatic, aliphatic or cycloaliphatic hydrocarbons or halohydrocarbons, dialkylethers, alkylnitriles, at a temperature ranging from 60 to 180 C, preferably at the boiling point of the solvent, distilling the azeotropic mixture alcohol-solvent and the dialkylamine which are formed. It is better to use an excess of (III), preferably 2-4 mol/mol of (II). After evaporation of the solvent under reduced pressure, the derivates (IV) are directly isolated, generally as very pure oils. Such derivates are new (excluding the 1-ethylderivative described in US 4085106) and they too are part of the present invention. Alternatively, the tricyclic compounds (IV) are obtained by alkylating the unsubstituted octahydro- tetraazacyclooctapentalen (V) whith the above mentioned -L-X compounds: (V) Compound (V) is formed by 1,4,7,10- tetraazacyclododecane and dimethylformamide- dialkylacetal, as disclosed in US 4085106. The hydrolysis of derivatives of formula (IV) is obtained by heating the mentioned compounds in a hydroalcoholic solution (preferably water/methanol or water/ethanol) . The ratio water/alcohol ranges from 1:3 and 3:1 (v/v) , and preferably is 1:1. The reaction temperature is not critical, it can range from room to reflux temperature. When the hydrolysis is finished, the solvent is removed under reduced pressure and the compounds of formula (I) are isolated from the residue by means of crystallization or chromatography. The following examples relate to the process according to the present invention. EXAMPLE 1 1-Benzyl-l,4,7,10-tetraazacyclododecane A solution of benzyl bromide (4.96 g; 0.029 mol) in acetonitrile (50 ml) is added in 1 h to a solution of 1,4,7 ,10-tetraazacyclododecane (50 g, 0.29 mol) in acetonitrile (450 ml) at refluxing temperature of the solvent and under inert atmosphere. After 30 minutes from the end of the addition, the reaction mixture is cooled at 5 C and part of the 1,4,7,10-tetraazacyclododecane in excess precipitate. After filtration, the reaction mixture is evaporated under reduced pressure. The residue, dissolved in 5% aqueous solution of sodium carbonate (200 ml), is extracted with toluene (3x200 ml). The organic phase is washed with water (100 ml), anhydrified (Na 2 S0 4 ) and evaporated to dryness. After crystallization by petrol ether (m.p. 40-60 C) , the desired product is obtained (6.8 g) as a white solid. Yield 89%. m.p. : 85 C. Titre : 98% (G.C.) 1 H-NMR (CDC1 3 ) : 2.4 ( , 8H) ; 2.5 (m, 4H) ; 2.6 (bt, 4H); 3.4 (bs, 2H) ; 7.2 (bm, 5H) . 13 C-NMR (CDC1 3 ): cT 44.90; 46.13; 46.98; 51.03; 59.04; 126.84; 128.11; 128.80; 138.74. M.S. (El) : 262 (M + ') Elemental Analysis for C, c H 2g N 4 (%) : Using the same procedure the following compounds were prepared: a) 1-hexadecyl-l,4,7,10-tetraazacyclododecane Colourless oil. Yield 82%. Titre : 99% (G.C.) 1 H-NMR (CDC1 3 ) : cT l.OO (bt, 3H) ; 1.25 (bs, 28H) ; 2.4- 3.0 (m, 18H). 13 C-NMR (CDC1 3 ): J 13.96; 22.53; 27.4-29.6; 31.79; 45.16; 46.08; 47.03; 52.30; 54.42. M.S. (El) : 396 (M + * ) Elemental Analysis for C 2 4 H 52 N 4 • ^ : C H N Calculated 72.66 13.21 14.12 Found 72.44 13.31 13.82 b) 1-dodecyl-l,4,7,10-tetraazacyclododecane Colourless oil. Yield 86% Titre : 96% (G.C.) 1 H-NMR (CDC1 3 ) : ςf1.0 (t, 3H) ; 1.45-1.55 (bs, 20H) ; 2.5-3.2 (m, 18H) 13 C-NMR (CDCL 3 ): cfl4.00; 22.55; 26.60-29.60; 31.80; 44.74; 45.63; 46.60; 51.11; 54.29 M.S. (El) : 340 (M +* ) Elemental Analysis for C Q H 44 N 4 (%) : C H N Calculated 70.50 13.04 16.45 Found 70.01 12.96 16.28 c ) 1-octyl-l,4,7,10-tetraazacyclododecane Colourless oil. Yield 86% Titre : 96% (G.C.) ^-NMR (CDC1 3 ) : <J 0.6 (br, 3H) ; 1.1 (m, 10H) ; 1.22 (m, 2H) ; 2.2-2.4 (m, 14H) ; 2.6 (m, 4H) 13 C-NMR (CDC1 3 ): fl2.96; 21.47; 26.2-28.3; 30.66, 44.02; 44.97; 45.91; 50.41; 53.28. M.S. (El) : 284 (M + ') Elemental Analysis for C lg H 36 N 4 (%) : C H N Calculated 67.52 12.77 19.69 Found 66.84 12.64 19.49 d) 1-[t-butoxycarbonyl)methyl3-1,4,7,10-tetraazacy- clododecane Colorless oil. Yield 58% Titre : 97% (G.C.) X H-NMR (CDC1 3 ) : l.75 (s, 9H) ; 2.85-3.15 (bm, 16H) ; 3.57 (bs, 2H) 13 C-NMR (CDC1 3 ): cf27.92; 44.99; 45.80; 46.71; 51.54; 56.78; 90.65; 170.08 M.S. (El) : 286 (M + ') Elemental Analysis for c i4H 30 4 O 2 (%): 1-[2-(1,3-dioxol-2-yl)ethyl]-1,4,7,10-tetraazacyclodo- decane A solution of 2-(2-bromoethyl)-l,3-dioxolane (16.08 g; 0.087 mol) in acetonitrile (1 1) is added in 2 h to a solution of 1,4,7,10-tetraazacyclododecane (150 g; 0.87 mol) in acetonitrile (2 1) at refluxing temperature and under inert atmosphere. After 30 minutes from the end of the addition, the reaction mixture is cooled at 5 C and the precipitate obtained is removed by filtration. After evaporation of the solution under reduced pressure, the residue is solubilized in boiling ethyl acetate. When the solution is cooled at 5 C, another part of 1,4,7,10- tetraazacyclododecane precipitates. After filtration, the solvent is evaporated under reduced pressure and the residue is purified by column chromatography [Silica gel; iεopropanol/chloroform/triethylamine = 6/4/2 (v/v/v)]. The product obtained is a colourless oil (20.8 g) . Yield 88%. Titre : 96% (G.C.) ^-H-NMR (CDC1 3 ) : cfl.9 (m, 2H) ; 2.6-2.7 (m, 14H) ; 2.8 ( , 4H) ; 3.8-4.0 ( , 4H) ; 4.9 (t, 1H) 13 C-NMR (CDC1 3 ) : c5 " 31.05; 44.58; 45.69; 46.53; 48.76; 50.96; 64.29; 102.93 M.S. (El) : 272 (M + ') Elemental Analysis for C,3H 2g 4 0 2 (%) : C H N Calculated 57.30 10.38 20.57 Found 56.93 10.48 20.77 By using the same procedure the following compounds were prepared: a)l-[ (1 ,3-dioxol-2-yl)methyl3-l,4 ,7 ,10-tetraazacyclodo- decane Colourless oil. Yield 85% Titre : 97% (G.C.) ^ ■ H-NMR (CDC1 3 ) : cT2.7-3.0 (m, 18H) ; 4.0-4.2 (m, 4H) ; 5.1 (t, 1H) 13 C-NMR (CDC1 3 ) : cT44.81; 45.94; 46.62; 51.92; 56.68; 64.45; 103.06 Elemental Analysis for c i2 H 26 N 4 0 2 ^•' : C H N Calculated 55.76 10.16 21.68 Found 56.43 10.34 21.92 b) 1-[2,2-( imethoxy)ethyl]-1,4,7 ,10-tetraazacyclodo- decane Colourless oil. Yield 90% Titre : 98% (G.C.) ^- MR (D 2 o) : cf2.4-2.7 (m, 18H) ; 3.4 (b, 6H) ; 4.45 (t, 1H) 13 C-NMR (D 2 o) : ςT46.16; 47.48; 47.90; 54.28; 57.21; 58.26; 106.81 Elemental Analysis for c ι 2 H 28 4 0 2 ( ) : 1-triphenylmethyl-1,4,7,10-tetraazacyclododecane A solution of triphenylchloromethane (8.08 g; 0.029 mol) in acetonitrile (250 ml) is added in 2 h to a solution of 1,4,7,10-tetraazacyclododecane (50 g; 0.29 mol) in acetonitrile (500 ml) at 40 C under inert atmosphere. After one hour from the end of the addition, the reaction mixture is cooled at 5 C and part of 1,4,7,10- tetraazacyclododecane in excess precipitates. After removing the solid by means of filtration, the reaction mixture is evaporated under reduced pressure and the residue is diluted with water (500 ml). The resulting suspension is filtered and the solid is washed with water (500 ml). After purification by column chromatography [Silica gel; ethyl acetate/6N ammonia in methanol -= 3/1 (v/v)] the desired product is obtained as a white glass solid (9.1 g) . Yield 75% m.p. : 70-71 C ^ ■ K-NMR (CDC1 3 ) : cT2.9-3.5 (m, 16H) ; 7.5-8.3 (m, 15H) 13 H-NMR (CDC1 3 ): cf43.60; 47.29; 49.47; 54.42; 79.37; 126.13; 127.55; 129.95; 143.72 Elemental Analysis C 2 7H 34 4 (%) : Calculated Found 7-benzyl-octahydro-5H,9bH-2a,4a,7,9a-tetraazacyclo- octa [cd]pentalene A solution of l-benzyl-1 , 4 , 7 , 10- tetraazacyclododecane (4 g; 0.015 mol) and dimethylformamide diethylacetal (6.88 g; 0.0467 mol) in benzene (40 ml) is heated at 80 C and the azeotropic mixture ethanol-benzene is distilled away. When the conversion is ended, the solvent is evaporated under reduced pressure and the final product is obtained as a yellow oil (4.0 g) . Yield 96% Titre : 100% (G.C.) 1 H-NMR (CDC1 3 ) : J 2.3-3.0 (m, 16H) ; 3.6 (s, 2H) ; 5.0 (s, 1H) ; 7.1-7.3 (m, 5H) 13 C-NMR (CDC1 3 ): cJ" 50.93; 51.86; 52.42; 55.25; 63.28; 97.73; 126.76; 127.97; 129.09; 139.62 Elemental Analysis for C-,gH 14 N 4 ( ) : following compounds were prepared: a) 7-[t-butoxycarbonyl)methyl]-octahydro-5H,9bH-2a,4a, 7,9a-tetraazacycloocta[cd]-pentalene Colourless oil. Yield 95% Titre : 99% (G.C.) ^-H-NMR (CDC1 3 ) : cf l.75 (s, 9H) ; 2.8-3.35 (m, 16H) ; 3.65 (s, 2H); 5.2 (s, 1H) 13 C-NMR (CDC1 3 ): cf27.79; 50.51; 51.77; 52.36; 54.64; 59.13; 80.16; 99.58; 170.66 Elemental Analysis for C,5H 2 oN 4 0 2 (%) : C H N Calculated 60.76 9.53 18.90 Found 60.15 9.43 18.71 b) 7-[2-(1,3-dioxol-2-yl)ethyl]-octahydro-5H, 9bH- 2a,4a,7 ,9a-tetraazacycloocta[cd]pentalene Colourless oil. Yield 95% Titre : 95% (G.C.) ■ " " H-NMR (CDC1 3 ) : rf " 1• 9 (m, 2H) ; 2.7-3.4 (m, 18H) ; 3.8- 4.0 (m, 4H); 4.9 (s, 1H) ; 5.2 (s, 1H) 13 C-NMR (CDC1 3 ) : 31.05; 49.84; 50.90; 51.98; 52.45; 55.23; 64.43; 98.48; 102.89 Elemental Analysis for C 14 H ?fi N 4 0 2 (%) : C H N Calculated 59.53 9.29 19.84 Found 60.13 9.41 20.24 c) 7-triphenylmethyl-octahydro-5H,9bH-2a,4a,7,9a- tetraazacycloocta[cd]pentalene 1 H-NMR (CDC1 3 ) : cT2.2-2.4 (m, 2H) ; 3.1-3.7 (m, 14H) ; 5.85 (s, 1H); 7.4-8.1 (m, 15H) 13 C-NMR (CDC1 3 ): ^51.50; 52.53; 53.29; 79.71; 98.58; 128.11; 127.56; 130.05; 143.90 Elemental Analysis for C 14 H 2 g 4 0 2 ( ) : C H N Calculated 59.53 9.29 19.84 Found 58.93 9.20 19.64 EXAMPLE 5 7-benzyl-l-formyl-1,4,7,10-tetraazacyclododecane A solution of 7-benzyl-octahydro-5H,9bH- 2a,4a,7,9a,tetraazacycloocta[cd]-pentalen (4 g; 0.015 mol) in water/ethanol 1:1 (v/v) (50 ml) is heated under reflux for 1 h. After evaporation of the solvent under reduced pressure, the residue is crystallized from ethyl acetate and the desired product is obtained (3.3 g) as a white solid. Yield 75%. m.p. 64-65 C Titre 96% (G.C.) 1 H-NMR (CDC1 3 ) cf2.6 (m, 8H) ; 2.7 (t, 2H) ; 2.9 (t, 2H) ; 3.4 (t, 2H) ; 3.5 (t, 2H) ; 3.6 (s, 2H);7.2-7.3 (m, 5H); 8.1 (s, 1H) 13 C-NMR (CDC1 3 ): ^44.40; 46.70; 46.80; 47.05; 47.30; 49.94; 50.5; 51.15; 59.39; 126.72; 128.03; 128.51; 139.51; 164.20 M.S. (El) : 290 (M +* ) Elemental Analysis for c ι gH gN 4 0 (%) : C H N Calculated 66.15 9.04 19.30 Found 66.21 9.06 19.28 Using the same procedure the following compounds were prepared: a) 7-[2-(1 ,3-dioxol-2-yl)ethyl3-1-formyl-1,4,7,10-te- traazacyclododecane Yield : 75% Titre : 96% (G.C.) 1 H-NMR (CDC1 3 ) : cT2.1 (t, 2H) ; 2.7-3.1 (m, 14H) ; 3.75 (m, 4H) ; 4.2 (bd, 4H) ; 5.2 (t, 1H) ; 8.1 (s, 1H) 13 C-NMR (CDC1 3 ) : cfl3.31; 44.37; 46.70; 46.84; 46.97; 47.1; 49.55; 49.99; 50.45; 51.02; 64.53; 102.82; 164.23 Elemental Analysis for i4H 28 N 4 0 3 (%) : b) 7-[(t-butoxycarbonyl)methyl-l-formyl-1,4,7,10- tetraazacyclododecane The compound is purified by means of column chromatography [Silica gel; methanol/28% aqueous ammonia - 10/1 (v/v) 3 Colourless oil. Yield 73% Titre : 95% (G.C.) ^-H-NMR (CDC1 3 ) : l. (s, 9H) ; 2.4-2.7 (m, 12H) ; 3.2 (s, 2H); 3.3-3.5 (m, 4H) ; 8.0 (s, 1H) 13 C-NMR (CDC1 3 ): 27.71; 43.23; 46.37; 46.70; 46.93; 49.57; 50.51; 51.70; 55.77; 80.38; 164.38; 170.68 Elemental Analysis for c χ5H 30 4 O 3 (%) :

Claims: CLAIMS 1. 1 , 7-disubstituted 1 , 4 , 7 , 10-tetraazacyclododecanes of formula ( I) : wherein : R is a for yl group or a derivative thereof, R*. is: a) a straight or branched alkyl group *-_-C 2 g, which is substituted or not by groups able to bind to proteins (for example OH, H 2 , COOH, CHO, SH and so on) or by their precursors (for example 0 2 , NO, CN, COOR and so on), b) an arylalkyl group C 7 -c 19 which is substituted or not on the aryl rest by one or more C,- C 4 alkyl, C* j _-C 4 alcoxy or halogen groups or by groups able to bind to proteins (for example OH, NH 2 COOH, CHO, SH and so on) or by their precursors (for example N0 2 , NO, CN, COOR and so on) 3 c) a group alkoxy(C***_- C 4 )carbonylmethyl or 2-[alkoxy(C 1 -C 4 )carbonyl3ethyl, d) a group of formula: -< CH 2>n- R 2 wherein n = 1-4 and 2 is a free or protected formyl group (for example an acetal group) or a precusor thereof. 2. 1,7-disubstituted 1,4,7,10-tetraazacyclododecane of formula (I) according to claim 1, wherein R, is alkyl C 6~ c 18' benzyl, triphenylmethyl, t- butoxycarbonylmethyl, or a group of formula _ ( H 2)n~ R 2 wherein n - 1 or 2 and R 2 is a group -CH(OCH3) 2 , - CH(OC 2 H 5 ) 2 or l,3-dioxol-2-yl. 3. Process for the preparation of compounds of claims 1-2, characterized in that said compounds are obtained by hydrolysis of the corresponding derivatives of formula (IV), which are obtained by reaction of R,- substituted tetraazacyclododecane of formula (II) with dialkylacetales of N,N-dialkylformamide of formula (III), or by alkylation of compounds of formula (V) with R-^-X compounds, according to the following reaction scheme: wherein R-, has the meanings given above, X represents a leaving group (preferably chlorine or bromine), and R 3 and R 4 , equal or different between them, are alkyl C-i- C 4 , preferably ethyl or methyl. 4 . Compound of general formula ( IV) which are useful for the preparation of compounds of formula (I) of claims 1-2.

Inventors: ANELLI PIER LUCIO, MURRU MARCELLA, UGGERI FULVIO, VIRTUANI MARIO, ANELLI, PIER, LUCIO, MURRU, MARCELLA, UGGERI, FULVIO, VIRTUANI, MARIO
Applicants: BRACCO IND CHIMICA SPA, BRACCO INDUSTRIA CHIMICA S.P.A.
Application year: 1991
Main classification: C07D257
IPC codes: C07D257, C07D405, C07D487