Sulfomethylation of di-, tri-, and polyazamacrocycles: a new route to

Sulfomethylation of di-, tri-, and polyazamacrocycles: a new route to entry of ... Correlation of Relaxivity with Coordination Number in Six-, Seven-,...
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Bioconjugate Chem. 1992, 3, 524-532

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Sulfomethylation of Di-, Tri-, and Polyazamacrocycles: A New Route to Entry of Mixed-Side-ChainMacrocyclic Chelates Jeroen van Westrenen and A. Dean Sherry' Department of Chemistry, The University of Texas at Dallas, P.O.Box 830688, Richardson, Texas 75083-0688. Received June 29, 1992

The sulfomethylation of piperazine and the polyazamacrocycles, [9laneN3, i121aneN3, [12laneN4, and [18]aneN6 with formaldehyde bisulfite in aqueous medium at various pH values is described. The number of methanesulfonate groups introduced into these structures was found to be largely determined by pH. At neutral pH, disubstituted products of [9laneN3, r121aneN3, [12laneN4 are formed and, in the latter case, the trans-1,7-bis(methanesulfonate)isomer was predominant. Similarly, a single, symmetrical trisubstituted product was formed with [181aneN6 a t neutral pH. Monomethanesulfonated products of these same polyaza compounds were formed at more acidic pH's. These sulfomethylated products were used as an entry into a series of mono- and diacetate, phosphonate, and phosphinate derivatives of [9]aneN3, [12laneN3, and C121aneN4. The sulfonate groups may be converted to acetates without isolation of intermediates by using cyanide to displace the sulfonate(s) followed by acidic hydrolysis. The aminomethanesulfonates may also be oxidatively hydrolyzed by using aqueous triiodide as a prelude to the preparation of aminomethanephosphonates or aminomethanephosphinates.

INTRODUCTION

The high thermodynamic stability and kinetic inertness of chelates formed between lanthanide(II1) cations and polyazamacrocyclic ligands having either carboxylate or phosphonate pendant donor groups have led to considerable interest in their application as NMR shift reagents in biological systems or as magnetic resonance imaging (MRI) contrast agents ( I ) . The protonation schemes that have emerged from prior potentiometric and NMR pH titrations show that these ligands have unique protonation patterns resulting from the close proximity of the ring nitrogens (2-7). The triazamacrocycles with ring sizes varing from 9 to 12 typically have one acidic nitrogen, one quite basic nitrogen, and a third nitrogen with a pK, near neutrality (Table 11). For polyazamacrocycles with an even number of nitrogens, such as tetraazacyclododecane and hexaazacyclooctadecane, a sharp division in pK,'s is shown upon half-protonation, To our knowledge, no advantage has been taken of these pK, differences in a synthetic sense. We considered that sulfomethylation may be especially well-suited for taking advantage of such pK, differences because the reaction is a Mannich-type reaction that works both in neutral and basic pH ranges (8)and indeed found that the sulfomethylation products of these polyazamacrocycles seem to be largely pH determined. We report here the synthesis of mono- and disulfomethylated triazamacrocycles, the preparation of a symmetrical disulfomethylated tetraazamacrocycle and a trisulfomethylated hexaazamacrocycle, and the conversion of several sulfomethylated products into carboxylate(s), phosphonate(81, or phosphinate(s). We show that sulfomethylation provides a convenient synthetic entry into selective geometrical isomers of macrocyclic chelates having more than one type of side-chain chelating group. RESULTS AND DISCUSSION

Sulfomethylation Using HOCH2S03Na. The sulfomethylation of amines by a Mannich-type reaction with

* Author to whom correspondence should be addressed.

formaldehyde and sodium bisulfite has been described previously. (9-13) The reaction may be carried out in aqueous solution using the commercially available sodium salt of formaldehyde bisulfite. The degree of sulfome-

thylation of macrocyclic amines was found to be quite pH dependent. For example, piperazine forms a disulfomethylated product at pH 9-10 and a monosulfomethylated product at pH 6 (see Table I). A similar pH selectivity was observed for sulfomethylation of the triazamacrocycles. Disulfomethylated [9laneN3 and [12laneN3 were obtained in high yields by using stoichiometric amounts of formaldehyde bisulfite at pH values between 7 and 9 (Table I), while monosulfomethylated products were formed exclusively at pH 4, even with formaldehyde bisulfite in a 3-fold excess over the amine. Trisulfomethylated products were only formed under conditions where all three macrocyclic nitrogens are known to be largely deprotonated (above pH 11-12). These observations suggest that protonation of a secondary amine dramatically decreases its reactivity with formaldehyde bisulfite and that the distinct PK, differences of the nitrogens within a given polyazamacrocycle give rise to this rather unusual chemical selectivity. The tetraazamacrocycle, [12laneN4, has two high and two low pK, values (Table 111, so at neutral pH, [121aneN4,2H+ is virtually the only ionic form present. As predicted, sulfomethylation of [12laneN4 with formaldehyde bisulfite at pH 7 yields the disulfomethylated product exclusively. Furthermore, of the two possible regioisomers, the 1,7-trans isomer is the predominant product (>go%1. This observation is consistent with the microprotonation sequence of [12laneN4 as determined by NMR (2),which indicates that the first two protonations occur at nitrogens trans to one another. Thus, at pH 7, two trans nitrogens are largely protonated while two remain nonprotonated and thus available to react with formaldehyde bisulfite. Regioisomers should also be formed in the reaction of 0 1992 Amerlcan Chemlcal Soclety

Sulfomethylatlon of DC, Trl-, and Polyaramacrocycles

Bloconjtgate Chem., Vol. 3, No. 6, 1992 121

Table I. Sulfomethylation Products and Yields of Di-, Tri-, and Polyazamacrocycles starting amine (A) piperazine

reactant (R) (mole ratio, R/A) HOCHzS03-Na+ (2.0)

conditions pH 9-10,70 "C, 2 h

% isolated Yield 51

product

n

Na+-O,SCHzNuNCHzSO~

Na'

1

piperazine

HOCHzS03-Na+ (1.05)

pH 6,40 OC, 2 h

51

A HN\NCHzS03H 2

191aneN3

HOCHzS03-Na+ (2.1)

[9laneN3

[9]aneN3

HzNCH~SO~-N (1.3) ~+

pH 9.5,40 "C, 16 h

>95

(a) pH 3.9,25 "C, 16 h (b) NaI/Iz

93

(a) pH 4,75 "C, 16 h (b) NaIIIz

50

7

[ 12laneN3

HOCHzS03-Nat (2.1)

pH 9.6, 40 "C, 16 h

n

Na+~ 0 3 S C H ~ y J z S O l -

Na'

>95

H 4

[12laneN3

HOCHzS03-Na+ (9)

pH 4,40 OC, 16 h

n

N a + - 0 3 S C H l i yJ,S03.

Na+

>950

H 4

(a) pH 4,3,25 "C, 16 h (b) NaI/Iz

[12]aneN3

NfiN. H

H.

CNS

65

'H5

CH,SO,H

0

[12laneN4

HOCH2S03-NaC(2.1)

pH 7,40 "C, 16 h

[HNnNcHzS03H 'I

HO3SCHzN

95

NH

U 5

[18laneN6

HOCHZSOa-Na+ (7.5)

pH 7,25 OC, 3 days

dTH rNH "1

53

H03SCHzN

CNJCHzs03H 6

Estimated from 13C NMR.

formaldehyde bisulfite with [18laneN6, yet the symmetrical1,7,13-trisubstitutedderivative was the main product observed when the reaction was carried out a t pH 7. Again, this likely occurs because three nitrogens are largely protonated at this pH (Table 11) and one might expect that the three protonations would occur at nitrogen

positions which give the least electrostatic repulsions. Interestingly, when this reaction was carried out in a Na2HPOa and KHzPOd buffer, trisulfomethylated [181aneN6 crystallized from the reaction mixture as a HP042-adduct. Sulfomethylation by Amine Exchange with (CH& NCHzSOsH. As indicated above, monosubstituted de-

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Table 11. Protonation Constants of Amines (25 "C) amine logK1 logKz logK3 logK4 (CH3)zNH 10.77 piperazine 9.83 5.56 [9]aneN3" 10.42 6.82 low [121aneN3" 12.60 7.57 2.41 [121aneN4b 10.6 9.6 low low [181aneN6' 10.07 9.11 8.61 3.97 a 0.1 M KN03,ref 6. b 0.1 M NaC104, ref 26. 0.1 M NaC104, refs 5 and 26.

rivatives of [9]aneN3 and [12landN3 may be synthesized at pH 4 in the presence of excess formaldehyde bisulfite. When 1.5 mol of formaldehyde bisulfite per [12laneN3 was used, only 30% of the amine was converted to a monosubstituted product during a 16 h period at 50 "C. Longer reaction times at this temperature leads to extensive decomposition of the desired product, as indicated by 13C NMR. Alternatively, (dimethylamino)methanesulfonic acid may be used as a sulfomethylating agent via an amine exchange reaction.

The reaction of [9]aneN3 with 1.5 equiv of (dimethy1amino)methanesulfonic acid at pH 3.8 shows complete conversion to the monosulfomethylated product plus dimethylammonium ion after 16 h at 25 "C, as indicated by NMR. This reaction likely proceeds via a reverse Mannich-type reaction, with the iminium ion or its hydrated form reacting with a nonprotonated triazamacrocyclic amine to liberate the dimethylammonium ion. The resulting macrocyclic iminium ion could then react with hydrogen sulfite to form the macrocyclic aminomethanesulfonate. The large pK differences between dimethylamine and the pKis of [9laneN3 or [12laneN3 (Table 11) result in an equilibrium which lies heavily in favor of the monosulfomethylated macrocycle at pH 4. The commercially available aminomethanesulfonic acid also undergoes an amine exchange reaction, but the rate of exchange is slower. After stirring of [9laneN3 with 1.3 equiv of aminomethanesulfonic acid at 25 "C, pH 4, for 16 h, about 50% of the starting amine was converted to a monosubstituted product. The rate of this exchange might be affected by the low solubility of aminomethanesulfonic acid, however, since this compound has limited solubility in water. Conversion of Aminomethanesulfonates to Aminomethanecarboxylates. The conversion of aminomethanesulfonates to amino acids via nucleophilic substitution of cyanide for sulfonate has been known for some time. (13-15) Cyanide substitution can be performed at 25 "C without isolation of the sulfomethylated product by adding NaCN directly to the reaction mixture. (13) After stirring of 1.5 equiv of NaCN with monosulfomethylated [9laneN3 (prepared in situ) for 16 h at room temperature, a 13CNMR spectrum of the reaction mixture indicates that N-(cyanomethyl)-l,4,7-triazacyclononane was the main product formed, with about 15-20% of unsubstituted 191aneN3 remaining. Both dimethylamine and a small amount of (CH3)2NCHzCN [formed by CNsubstitution with (dimethy1amino)methanesulfonicacid] were present in the reaction mixture as well. The desired product was purified by cation-exchange chromatography in an isolated yield of 32 % . Subsequent hydrolysis of the nitrile in HC1was followed by 'H NMR. Refluxing the nitrile for 30 min in 20 5% HCl

van Westrenen and Sherry

regenerates about 25% of the original amine, [9laneN3. Reducing either the temperature or the acid concentration reduced the amount of decarboxylation but led to extended reaction times for the hydrolysis. Since reformation of at least some [9]aneN3 appeared inevitable during acidic hydrolysis, a one-pot synthesis of 1,4,7-triazacyclononaneN-acetic acid was developed with the optimum hydrolysis conditions being about 10% HC1,75 "C, for 4 days. These conditions gave the monoacetic acid derivative in an isolated yield of 32 % ,after purification by cation-exchange chromotography (see Table 111). As noted above, formaldehyde bisulfite was used for disulfomethylation of the triaza and tetraaza macrocycles. acid, which Unlike (N,N-dimethy1amino)methanesulfonic forms unreactive (CH3)zNCHzCN during nucleophilic displacement by CN-, the formaldehyde adduct forms HOCHzCN under similar conditions (confirmed by l3C NMR in a separate experiment) and this is known to react with free amines to give aminomethanenitriles. (16,17) The reactivity of HOCH3CN was particularly evident during the conversion of disulfomethylated [12laneN3 to the dinitrile. When 112laneN3 was sulfomethylated by using 4 mol of formaldehyde bisulfite per mole of [121aneN3 in a concentrated buffer medium a t pH 7, 13CNMR indicated that the major product was disulfomethylated [12]aneN3. However, upon addition of 4 mol of NaCN to this same reaction mixture, the tricyanomethylated derivative of [12laneN3 crystallized from the reaction mixture in 52 5% yield. The same phenomena was observed when [12laneN4 was reacted with 5.5 mol of formaldehyde bisulfite at pH 7 followed by the addition of 5.5 mol of NaCN in a second step. In this case, the tetracyanomethylated derivative of [12laneN4 crystallized from the reaction mixture in 61 % yield. Therefore, if the desired product is a dicyanomethylated triaza- or tetraazamacrocycle, the cyanide substitution reaction must be carried out after formaldehyde bisulfite is completely consumed. Fortunately, disulfomethylated derivatives of [9laneN3, [12laneN3,and [12laneN4can be preparedquantitatively using stoichiometric amounts of formaldehyde bisulfite. Thus, the pure 1,7-diacetic acid derivative of [12laneN4 may be isolated in 80 % yield (after purification by cationexchange chromatography) by reacting [12laneN4 with 2 equiv of formaldehyde bisulfite at pH 7, adding NaCN without a reaction workup, followed by hydrolysis in refluxing 20% HC1 for 48 h (Table 111). The 1,4disubstituted regioisomer that is formed in small quantities during sulfomethylation is not detected by lH or 13CNMR after column purification. Acidic hydrolysis of the dicyanomethylated [12laneN4 product does not appear to require the same mild acidic conditions to prevent decarboxylation, for reasons that are not fully understood. This same reaction sequence has been used to prepare the diacetic acid derivative of [12laneN3 in 19% yield with 95% purity (Table 111). In this case, a small amount of the monoacetic acid derivative is present after purification by cation-exchange chromatography. The Reaction of Macrocyclic Aminomethanesulfonates with Triiodide. Disubstituted aminomethanesulfonic acids can undergo oxidative hydrolysis to aminomethanol derivatives by reaction with triiodide, the rate-limiting step being the formation of the sulfite ion via the reverse Mannich reaction prior to its oxidation to sulfate. (18) 'H NMR studies by Burg (19)have shown that the reaction of triiodide with Me2NCH~S03-proceeds almost quantitatively to MezNCHzOH in a few minutes as judged by NMR. Similarly, the reaction of bis(sulfomethy1)piperazinewith 2 mol of triiodide in aqueous

Sulfomethyletlon of DC, TrC, and Polyaremacrocycles

Bloconjugate Chem., Vol. 3, No. 6, 1092 127

Table 111. Summary of Reactions Used To Convert Sulfomethylated Polyazamacrocycles into Carboxylates, Phosphonates, or PhosDhinates ~~

~

sulfomethylated amine 7

reactant(s) and conditions (a) NaCN, DH 3.5 (b) 37% HCl, 75 "C, 4 days

% isolated yield 32

product

LH,CO,H

ryJ 11

molten H3P03,80 OC

21 *

2HCI

I

CH,P03H,

4

HP(O)(OEt)Et, 25 "C

43

HP(O)(OEt)z, 25 OC

24

(a) NaCN, 25 "C, 24 h (b) 20% HCl, reflux, 3 days

19

14

n

HP(O)(OEt)Z,25 OC

HN

31

NH,

HP(O)(OEt)Et,25 OC

73

21

n

(a) NaCN, 22 h, 25 OC (b) 37% HC1, reflux, 65 h

NCH,CO,H

[HN

1

80

'HCI

HozCCHzNUNH 15

(a) 10% HC1, NaI3, ppt, 25 "C (b) molten H3P03,80 "C, 3 h

24

n

[HN HN

]

NCH2P03H2 'HCI NH

W

22

solution at 25 "C resulted in a color change from brown to colorless after about 2 min. This event was followed by the formationof a white precipitate, which was isolated in 34% yield. An IR spectrum of the isolated solid showed a broad absorption from 2534 to 2342 cm-1, indicative of a protonated quaternary nitrogen. Elemental analysis was

consistent with formation of the dihydrated form of the diiminium ion. The addition of sodium triiodide to either monosulfomethylated[9laneN3 or [12laneN3resulted in formation of brown precipitates, which were isolated in high yields. These proved to be simple triodide salts of the monosulfomethylatedtriaza compounds, which have

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van Westrenen and Sherry

Bloconlugete Chem., Vol. 3, No. 6, 1992

limited water solubility at room temperature. The triiodidesalt of monosulfomethylated 191aneN3 does dissolve in water at 40 "C and this solution gradually becomes colorless over a 3-h period, indicating that triiodide had completely reacted with the monosulfomethylated amine. The expected hydrolysis product was confirmed by 'H NMR, which showed broad peaks for the [9laneN3 protons (3.61 ppm) and the NCHzOH methylene protons (4.58 ppm). Resonances at 4.81 and 3.69 ppm indicated that some further hydrolysis to HOCH20H and unsubstituted [91aneN3 had occurred. Dissolution and subsequent reaction of monosulfomethylated E121aneN3 goes even slower; complete oxidative hydrolysis was not observed after 16 h at 40 "C. It also proved possible to reduce the triiodide salt of monosulfomethylated [9laneN3 to iodide without altering the methanesulfonate group on the macrocycle by suspending the salt in ethanol and adding excess diethyl phosphite. Conversion of Aminomethanesulfonates to Aminomethanephosphonates and Aminomethanephosphinates. Although the mechanisms of sulfonate displacement by cyanide has not been described, other strong nucleophiles such as the malonate anion apparently react similarly. (13) However, the nucleophilicity of HP(=O)(0H)z or its conjugate base is too low to displace the sulfonate group as no phosphorylation seems to occur even with alarge excess of HP(=O)(OH)z. As indicated above, some aminomethanesulfonates may be converted to the corresponding aminomethanol derivatives, and these in turn are reactive intermediates in the Mannich reaction. As one example, the addition of a 10-fold excess of phosphorus acid to (CH&NCHzOH (formed in situ by reaction of MeZNCHZS03- with triiodide) gave quantitative yields of (dimethy1amino)methanephosphonateafter 4 h at reflux. Partial hydrolysis to dimethylammonium and formaldehyde was observed when a 5-fold excess of phosphorus acid was used. Oxidative hydrolysisof the disulfomethylated derivative of piperazine with triiodide gave a bis(hydroxymethy1)piperazine salt that precipitated from solution. Addition of 1mmol of this salt to a 10 M phosphorous acid solution resulted in the formation of di- (17% ) and monomethylenephosphonate (50% ) derivatives of piperazine plus free piperazine after 4 h a t reflux. However, this undesired reaction was prevented by carrying out the reaction in molten phosphorous acid at 80 "C. These conditions gave NJV-bis(methy1enephosphonate)piperazine as the only product (Table 111). The partially substituted methanesulfonate derivatives of the tri- and tetraaza macrocycles have an additional problem in that intermolecular reactions result in polymers. To suppress this side reaction, the phosphonylation was carried out in 20% ' HC1to insure that all amino groups were fully protonated. When the oxidized product of 1,7dieulfomethylated [12laneN4 was refluxed with a 10-fold excess of phosphorous acid per hydroxymethylene group, extensive hydrolysis of the hydroxymethylene group still occurred, giving a mixture of monomethylphosphonylated [12laneN4 and "free" f121aneN.l with no trace of the expected disubstituted methanephosphonate. Phosphonylation of the tri- and tetraazamacrocycles cannot be carried out under anhydrous conditions such as those descibed for the piperazine derivative because the aminomethanol derivatives are not isolated in pure form as a solid. However, the HI3 salts of the monomethanesulfonic acids of [9laneN3 and 1121aneN3 may be used directly. When these triiodide salts were added to molten phosphorous acid at 80 "C or to neat HP(=O)Et(OEt)or

HP(=O)(OEt)2at 25 "C, exothermic reactions occurred, yielding the monomethanephosphonate, the monomethaneP-ethylphosphinate ethyl ester, and the monomethanephosphonate diethyl ester, respectively, of [9laneN3 and [12laneN3 nearly quantitatively within a few seconds (Table 111). The yields reported in Table I11 are isolated yields of the pure compounds. Isolation of the pure product is somewhat more elaborate due to the presence of a large excess of H-P compound and small amounts of the unsubstituted product. Both the monomethanephwphonate diethyl ester and the monomethane-P-ethylphosphinate ethyl ester of [9]aneN3 crystallized in pure form in ethanol. The corresponding [12laneN3 derivatives are more soluble in ethanol whereas unsubstituted [12laneN3 precipitated in ethanol. N-Methylation products that are commonly observed as side products in a Mannich reaction involving H-P compounds were not detected by 'H NMR in these reactions. This makes this a very attractive method for preparing monomethylphosphonylated and monomethylphosphinated triazamacrocycles. The yields could undoubtedly be improved upon by altering the workup procedure. CONCLUSIONS

Sulfomethylation of di-, tri-, and tetra-, and hexaazamacrocyclic amines may be carried out successfully over a wide pH range, from 3 to 11. The selectivityof this reaction appears to arise from the substantial pK, differences of the nitrogens in these polyazamacrocycles. Monosubstituted products may be obtained in high yields at pH 4 while regioselective partially substituted products may be obtained at pH 7. At neutral pH, a sharp division of pK,)s for 1121aneN4 and [18laneN6 results in selective formation of disubstituted [ 12laneN4 and trisubstituted [18laneN6. In each case, the nitrogens were sulfomethylated in alternating positions as evident by NMR. This is consistent with the premise that microscopic protonation of the macrocyclic nitrogens determines the degree of sulfomethylation. (Dimethy1amino)methanesulfonate was also found to donate sulfomethyl groups selectively to nonprotonated amines in [9laneN3 or [12laneN3,thus providing a simple synthetic route to the monosulfomethylated analogs. It was also possible to oxidatively hydrolyze the sulfomethylated piperazines, monosulfomethylated [9laneN3, and, to a lesser extent, monosulfomethylated [12laneN3 using triiodide. Surprisingly, monosulfomethylated [91aneN3 and [12laneN3 react so slowly with triiodide that these compounds may be isolated as stable triiodide salts. Although there may be no obvious advantage of using this method over direct alkylation methods to prepare mono- or diacetate derivatives of a triaaza macrocycle (20), it does offer the versatility of preparing a variety of monoand disubstituted phosphonate, phosphonate monoester, and alkyl phosphinate derivatives of the triaza macrocycles which may be difficult to prepare using more direct methods. One major advantage of the sulfomethylation route became evident by the observation that alternately substituted tetraaza and hexaaza macrocycles were prepared easily in excellent yields, without the use of amine protective groups. There has been considerable interest in preparing the triacetate derivative of [12laneN4 (D03A) (21) in bulk quantities as a starting material for MRI contrast agents. Dischino, et al. (22) obtained D03A in 26% yield by the direct alkylation route (which produces a mixture of products that must be separated by ionexchange chromatography) versus in approximately 69 %

Sulfomethylatlon of DC, TrC, and Polyazemacrocycles

yield via a monoformyl tetraaza macrocyclic intermediate. The preparation of particular disubstituted geometric isomers of [12]aneN4 is even more problematical. For example, Aime et al. (23)have recently reported isolating both the cis and trans isomers of a particular dialkylated [12laneN4 in 25% and 8% yield, respectively. Another very recent report (24)describes the preparation of several trans-1,7-diprotected [12laneN4 derivatives in yields ranging from 49% to 77%. The method presented here allowspreparation of the trans-l,7-bis(methanesulfonate) [12laneN4 product in about 90% yield which, in turn, may be converted to a variety of products (acetates, phosphonates, phosphinates, etc.) with differing chelating tendencies. EXPERIMENTAL PROCEDURES The macrocycles 1,4,7-triazacyclononane ([9laneN3), 1,5,9-triazacyclododecane([12laneN3), [ 12laneN3*3HBr, 1,4,7,10,13,16-hexaazacyclooctadecane([18laneN6), and [18]aneN6.3H2S04, the formaldehyde sodium bisulfite addition compound, aminomethanesulfonic acid, dichloroethylphosphine, and diethyl phosphite were obtained from Aldrich Chemical Co. (Milwaukee, WI). 1,4,7,10Tetraazacyclododecane tetrahydrochloride (1121aneNG4HCl) was obtained from Parish Chemical Co. (Orem, UT). (Dimethy1amino)methanesulfonicacid was prepared in 40 % yield with a 92 7% purity (iodometricassay) according to a modified Backer and Mulder procedure (9). All NMR spectra were recorded on a JEOL JNMFX200; the methyl group of tert-butyl alcohol was used as internal reference at 1.2 ppm (1H NMR) or at 31.2 ppm (13C NMR). Elemental analysis were performed by ONEIDA Research Service, Inc. Disodium Piperazine-NJV-bis(methanesu1fonate) (1). An aqueous solution (5 mL) containing piperazine (10 mmol, 0.86 g) and HOCH2S03Na (20 mmol, 2.68 g) was heated for 2 h at 70 "C. The precipitate which formed was filtered off and washed with ethanol (10 mL) and ether (10 mL). The product was obtained in 51% yield (1.79 g). lH NMR (D2O): 3.81 (s,4 H), 2.91 ppm (s,8 H). 13C NMR (DzO): 73.0, 51.5 ppm. Anal. Calcd for CeHlzN2S206Na2.2H20: C, 20.34; H, 4.55; N, 7.91; S, 18.10. Found: C, 20.34; H, 4.54; N, 7.82; S, 18.22. Piperazinomethanesulfonic Acid (2). An aqueous solution (3 mL) containing piperazine (2 mmol, 0.172 g) neutralized with hydrochloric acid (2 mmol) and HOCH2S03Na (2.1 mmol, 0.282 g) was heated for 2 h at 40 "C. Ethanol (10 mL) was added to the solution and after a few hours a white product crystallized. The crystals were suitable for X-ray diffraction. (25)Yield 51% (1.02 mmol, 0.188g). lH NMR (D2O): 3.82 (s,2 H), 3.24 (m, 4 H), 3.12 ppm (m, 4 H). 13C NMR (H20/D20): 72.95,49.14,44.27 ppm. Anal. Calcd for CsHlzN2S0~0.25H20:C, 32.51; H, 6.77;N,15.16;S,17.36. Found: C,32.63;H,6.59;N,15.25; S, 19.03. Hydrogen Sodium 1,4,7-Triazacyclononane-N,Nbis(methanesu1fonate) (3). [9laneN3~3HCl(1 mmol, 0.239 g) was dissolved in water (3 mL), neutralized with NaOH (1.342 mL, 1.49 M), and mixed with HOCH2S03Na (2.1 mmol, 0.282 g). The final solution pH was 6.9. After heating for 16 h at 40 "C the reaction was complete. Ethanol (10 mL) was added and the product slowly crystallized. The crystals were filtered and washed with ethanol and ether to yield 97 % (0.373 g). Recrystallization in 50/50watedethanol gave crystals that were suitable for X-ray diffraction. (25) lH NMR (D2O): 3.98 (s,4 H), 3.17 (s,8 H), 3.01 ppm (s,4 HI. 13CNMR (D2O/H20): 73.58, 51.76, 49.36, 46.07 p p m . A n a l . C a l c d f o r

Bioconlugate Chem., Vol. 3, No. 6, 1992 529

CsH18N&O6Na-2.5H20: C, 25.00; H, 6.03; N, 10.93; S, 16.68. Found: C, 24.81; H, 5.78; N, 10.85; S, 17.45.

Disodium 1,5,9-Triazacyclododecane-N,N"-bis(methanesulfonate) Hydrochloride (4). [121aneN3 (1.206 mmol, 0.206 g) was dissolved in water (3 mL), neutralized with HCl(l.047 mL, 1.152 M), and mixedwith HOCH2S03Na (2.533 mmol, 0.340 g). The final solution pH was 9.6. The reaction was complete after 16 h at 40 "C. Ethanol was added and the solution was evaporated in vacuo a t 40 "C. The resulting precipitate was treated with acetone (50 mL), filtered, and washed with ether, Yield: 98% (0.540 g). lH NMR (D2O): 3.74 (s,4 H), 3.13, 3.03,2.78 (bs, 4 H), 1.88 ppm (bs, 6 H). 13CNMR (D2O/ H2O): 69.0, 55.48, 48.40, 47.58, 23.20, 22.40 ppm. Anal. Calcd for C I I H ~ ~ N ~ S ~ O ~ N ~ T HC,C 28.85; ~ . H ~H, O :5.72; N, 9.18; S, 14.00. Found: C, 28.83; H, 5.49; N, 8.25; S, 13.89.

1,4,7,1O-Tetraazacyclododecane-NJT'-bis(methanesulfonic Acid) (5). [12laneN4-4HC1(1mmol, 0.318 g) was dissolved in water (3 mL), neutralized with NaOH (1.342 mL, 1.49 M), and mixed with HOCH2S03Na (2.1 mmol, 0.282 g). The final pH of the mixture was 7. After heating for 16 h at 40 "C the reaction was complete. Ethanol (10 mL) was added and the reaction mixture was evaporated. Addition of fresh ethanol gave an oil that slowly crystallized. The crystals were filtered and washed with ethanol and ether to yield 0.565 g (95%). Sodium chloride was present in the solid as well. The ratio of 1,7-disubstituted:l,4-disubstitutedwas about 9:l. The product was further purified by fractional recrystallization in ethanol/water. NaCl crystallized first, whereafter adding extra ethanol to the reaction mixture produced large needle-shaped crystals of pure l,7-disubstituted product which were suitable for X-ray diffraction. (25) lH NMR (DzO): 3.83 (s,4 H), 3.12 (s,16 HI ppm. 13CNMR (D2O/H20): 71.61, 51.56, 45.67 ppm. Anal. Calcd for C~OH~~N~S~O C,V30.29; ~ H ~H,O7.12; : N, 14.13. Found: C, 30.25; H, 7.05; N, 13.98. 1,4,7,10,13,16-HexaazacyclooctadecaneN,N",lV""tris(methanesu1fonate) (6). [18laneN~3HzS04(1"01, 0.556 g) was dissolved in water (10 mL) and neutralized with NaOH (2.105 mL, 1.424 M). HOCH2S03Na (7.53 mmol, 1.01 g) and NazHPO4/KHzP04 (pH 7 buffer: pHydrion dry, 4.85 g) were added. The mixture was stirred a t room temperature for 3 days, during which time a product crystallized from solution. The product was filtered off and washed with ethanol (50 mL) and ether (50 mL). Yield: 52.5% (0.284 g). 'H NMR (DzO): 3.93 (8, 6 H), 3.30 (bs, 12 H), 3.18 ppm (be, 12 H). 13C NMR (D2O): 69.83, 53.20, 47.64 ppm. Anal. Calcd for Cl5H36NsS3O13K3'H3PO4'1.5HzO:C, 23.10; H, 5.06; N, 10.81; S, 12.37. Found: C, 23.24; H, 5.28; N, 10.66; S, 12.30. 31PNMR (HzO, pH 7, ref 85% H3P04/H20): 1.66 PPm1,4,7-Triazacyclononane-N-methanesulfonate Hydrotriiodide (7). [9]aneN3 (8.79 mmol, 1.136 g) was dissolved in water (10 mL) and 17.6 mL of 1.0 M HC1 added followed by 1.84 g of (C!H~)ZNCH~SO~H. The pH of the resulting mixture was 3.8. After 16 h at 25 "C the reaction was complete. l3C NMR (D20/H20): 72.93,50.93, 45.81, 44.10, 36.43 ppm ((CH3)2NHz+). lH NMR (D20): 4.026 (8, 2 H), 3.689 (8, 2 H), 3.347 (bs, 8 H), 2.692 ppm (s, 6 H, (CH3)2NH2+).An aqueous solution (7 mL) containing iodine (13.21 mmol, 3.353 g) and sodium iodide (26.42 mmol, 3.96 g) was added to the reaction mixture. Almost immediately, a brown precipitate was formed. The precipitate was filtered off and washed with ethanol (50 mL) and ether (50 mL), yielding brown crystals in 93%

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Bloconlugate Chem., Vol. 3, No. 6, 1992

van Westrenen and Sherry

yield (4.492 g). Anal. Calcd for C ~ H ~ ~ N ~ S O ~ I T O . ~ Addition H ~ O : of 3 mL of ethanol to the filtrate gave a white precipitate (0.418 g), which was further purified using C, 13.69; H, 3.12; N, 6.84; S, 5.22. Found: C, 13.69; H, Dowex 50x8 (bed volume, 9 mL). Absolute ethanol (10 3.01; N, 6.70; S, 5.53. mL) was added to the fraction containing the product, 1,4,7-Triazacyclononane-N-methanesulfonatehydrowhereupon a white solid was formed. The solidwas filtered triiodide can be reduced to the hydroiodide salt by diethyl off and washed withethanol and ether. Yield: 32% (0.259 phosphite. The13 salt (0.11mmol, 66.7 mg) was suspended g). 'H NMR (D2O): 3.66 (8, 2 H), 3.62 (8, 1 H), 3.30 (t, in ethanol (0.5mL) and HP(O)(OEt)z (21.3 pL) was added. 2 H, 3J = 6.1 Hz), 3.09 ppm (t,2 H, 3 J = 6.1 Hz). 13CNMR The brown solid completely decolorized upon reaction. (DzO): 178.40,57.23,50.92,46.36,45.05ppm. Anal. Calcd The precipitate was filtered off and washed with ether (10 for C8H17N30~2HCl:C, 36.93; H, 7.36; N, 16.15. Found: mL). Yield: 35.79 mg. This salt was now readily soluble C, 36.66; H, 7.25; N, 15.89. in D2O. lH NMR (DzO): 3.98 (s,2 H), 3.67 (s,4 H), 3.33, Nfl,iV"-Tris(cyanomethy1)-1,5,9-triazacyclodode3.29 ppm (2 bs, 8 H). cane (12). [12laneN3 (1.52 mmol, 0.26 g) was dissolved 1,5,9-Triazacyclododecane-N-methanesulfo~~ Hyin 6.2 mL water and neutralized with a HC1 solution (1.32 drotriiodide (8). [12]ane*3HBr (2.42 mmol, 1 g) was mL, 1.15 M) followed by addition of pH 7 buffer (Metrepak dissolved in water (4 mL) and neutralized with NaOH pHydrion tablet, 0.75 g) and HOCH2S03Na (6.08 mmol, (1.696 mL, 1.424 M). After adding0.504g of (CH3)zNCHz0.815 g). The solution was stirred for 16h a t 25 "C followed S03H, the pH of the reaction mixture was 4.3. After 16 by addition of sodium cyanide (6.08 mmol, 0.298 g). The h at room temperature the reaction was complete. 13C reaction mixture was then heated to 50 "C for 6 h. The NMR (D20/H20): 70.78, 54.84,46.23,43.64, 23.27,21.63 product precipitated from the reaction mixture in pure ppm. A (CH&NHz+ resonance was present at 36.43 ppm. form. The white precipitate (0.173 g) was filtered off and An aqueous solution (2 mL) containing iodine (2.42 mmol, washed with water (5 mL, 0 "C). The pH of the remaining 0.61 g) and sodium iodide (4.83 mmol, 0.724 g) was added filtrate was adjusted to 10 by adding a few drops of 1 M and the HI3 salt was isolated as described for 7. Yield: 65% (1.0722 g). Anal. Calcd for C ~ O H Z ~ N ~ S O ~C, I ~ * H ~NaOH O : and the solution extracted with dichloromethane (3 X 50 mL). After evaporation of dichloromethane, the 18.06; H, 3.94; N, 6.32; S, 4.82. Found: C, 18.01; H, 3.62; residue was dissolved in water (5 mL). Smallwhite needleN, 6.33; S, 4.46. shaped crystals (0.0702 g) were formed over several hours. Piperazine-Nfl-bis( hydroxymethane)Sodium HyThe overall yield was 55% (0.243 g, 0.84 mmol). 'H NMR drogen Sulfate (9). Iodine (2.09 mmol, 0.530 g) and (CDCld: 3.54 (8, 1 H), 2.63 (t, 2 H), 1.65 (m, 1 H), 1.65 sodium iodide (2.00 mmol, 0.30 g) were dissolved in 4 mL ppm (8, 0.3 H, 1 HzO). 13C NMR (CDCl3): 115.4, 49.2, The iodine that did not dissolve was filtered of water. 42.7, 22.7 ppm. offer prior to the addition of disodium piperazine-N,"N,N,N',N''-Tetrakis( cyanomet hy1)-1,4,7,10-tetbis(methanesu1fonate) (1; 1.01 mmol, 0.322 g). Two raazacyclododecane(13). [12laneN4 (1.00 mmol,O.318 minutes after the addition, the solution turned clear and g) was dissolved in 2 mL of water and neutralized with a white precipitate formed. The crystals were filtered and NaOH (1.34 mL of 1.49 M). HOCHZSOZNa (5.50 mmol, washed with ethanol and ether. Yield: 34% (0.111 g). IR 0.738 g) was added and the reaction mixture was stirred (cm-l): 3459,3421 (O-H), 3026,2970 (C-H), 2534-2342 for 2 h at 25 "C. Sodium cyanide (5.5 mmol, 0.27 g) was (N+-H), 1629, 1463 (C-N). Anal. Calcd for added and the reaction mixture was stirred an additional C~H14N2Oz-NaHSOgO.25NaI-HzO: C, 22.40; H, 5.32; N, 3 days at 25 "C. The white precipitate that formed was 8.71; I, 9.86. Found: C, 22.50; H, 5.22; N, 9.10; I, 9.67. lH filtered off and washed with water (5 mL, 0 "C) and dried NMR (DzO): 4.02 (s, 4 H), 3.39 ppm (s, 8 H). under vacuum over HzS04. Yield: 61% (0.61mmol, 0.21 .N-(Cyanomethyl)-1,4,7-triazacyclononane Hydrog). lH NMR (CDC13): 3.59 (8, 1H), 2.76 ppm (s,2 H). 13C chloride (10). Triazacyclononane (2.32 mmol, 0.300 g) NMR (CDCl3): 114.8, 51.4, 43.54 ppm. was dissolved in 3 mL water and neutralized with HC1 (4.64 mL, 1.0 M). ( C H ~ ) Z N C H ~ S O (3.20 ~ H mmol, 0.485 1,5,9-Triazacyclododecane-N,N-diacetic Acid Hyg) was added to the solution to give a final pH of 3.1. The drochloride (14). 1,5,9-Triazacyclododecanetrihydroreaction mixture was stirred for 24 h at 25 "C. Sodium bromide (0.414 g, 1mmol) was dissolved in 3 mL of water cyanide (3.483 mmol, 0.171 g) was added and the reaction and neutralized with NaOH (1.342 mL, 1.49 M). HOCH2mixture was stirred for another 16h at 25 "C. The reaction S03Na (0.268 g, 2 mmol) was added and the reaction product was purified on Dowex 50x8 (bed volume, 25 mL). mixture was heated for 16 h at 40 "C. Sodium cyanide A 25-mL portion of ethanol was added to the oily residue (0.103g, 2.1 mmol) was added and the mixture was stirred obtained from the column to yield the pure product as a for 24 h a t 25 "C. 13CNMR (DzO/HzO): 117.5,56.6,51.1, white powder. Yield: 33% (0.187 g). 'H NMR (DzO): 50.2,48.3,23.2,22.9 ppm. The reaction was worked up by 4.013 (s, 1H), 3.79 (s,2 H), 3.54 (t, 2 H, 3J = 6.1 Hz), 3.23 adding NaOH (1.4 mL, 1.49 M) and the product was ppm (t, 2 H, 3 J = 6.1 Hz). 13C NMR (DzO/HzO): 118.0, extracted into dichloromethane (3 X 100 mL). The 49.61, 45.18, 44.04 p p m . A n a l . C a l c d f o r dichloromethane was removed by evaporation under CeH14N4*1.5HC1-1.5HzO: C, 38.75; H, 7.52; N, 22.60. vacuum and the residue was dissolved in 20 mL of HC1 Found: C, 38.99; H, 7.56; N, 22.71. (20%) and refluxed for 3 days. The solution was evaporated under vacuum and the excess HC1 was removed by 1,4,7-Triazacyclononane-N-acetic Acid Hydrochlocoevaporation with 10 mL of water. The product was ride (11). Compound 10 was prepared as described above purified on Dowex 50x8 (bed volume 5 mL). The solid starting from [9laneN3 (3.075mmol, 0.397 g) and (CH& obtained after lyophilization was dissolved in 3 mL of NCHzS03H (4.61 mmol, 0.642 g) at pH 3.5. Sodium ethanol and precipitated upon addition of 20 mL of ether. cyanide (4.24 mmol, 0.227 g) was added. After the The white solid was filtered off and washed with ether. substitution was complete, the reaction mixture (10 mL) Yield: 19% (0.084 g). 'H NMR (DzO): 3.73 (s,4 H), 3.12 was directlyacidified with4 mL of concentrated HCl(37 % ) (m, 12 H), 2.00 (m, 4 H), 1.97 ppm (m, 2 H). 13C NMR and heated at 75 "C for 4 days. The solution was (D20): 172.2,56.67,53.92,52.08,45.86,21.84,21.30ppm. evaporated under vacuum. After addition of 10 mL of The product was 95 5% pure as judged by 13CNMR (a small concentrated HCl(37 % 1, NaCl crystals were filtered off, amount of the monoacetate derivative was present). Anal. and the brownish solution was concentrated to 3 mL.

Sulfomethylation of DI-, TrC, and Polyaramacrocycles

Calcd for C13H2sN304-2.5HC1-3H20:C, 36.10; H, 7.81; N, 9.71. Found: C, 35.87; H, 7.86; N, 9.62. 1,4,7,10-Tetraazacyclododecane-N,lV-diacetic Acid Hydrochloride (15). [12laneN4*4HC1(1mmol, 0.318 g) was dissolved in 3 mL of water and neutralized with NaOH (1.34 mL, 1.49 M). HOCH2S03Na (2.1 mmol, 0.28 g) was added and the solution heated a t 40 "C for 16 h. 13CNMR indicated that approximately 90% the 1,7-bis(methanesulfonate) derivative and 10% of the corresponding 1,4isomer was present. Sodium cyanide (2 mmol, 0.098 g) was added. After 6 h at 25 "C an additional amount of sodium cyanide (0.5 mmol, 0.0243 g) was added and the reaction mixture was stirred for another 16 h. At the end of this period, 13CNMR showed that the l,'l-bis(cyanomethyl) derivative had formed. 13CNMR (D20/H20): 119.2, 51.52,45.51,45.15 ppm. Thereaction mixture was acidified by adding HCl(37 % ,20 mL) and the cyano groups were hydrolyzed by refluxing the solution for 65 h. The solution was evaporatedto dryness under vacuum and coevaporated with 2 X 20 mL of water. The product was purified on Dowex 50x8-200 (bed volume 20 mL). The product fraction was evaporated under vacuum and lyophilized. Ethanol (2 mL) was added to the solid and the white solid filtered and washed with 5 mL of ether. Yield 80% (0.314 g). l3C NMR (D20/H20): 176.3, 55.2, 50.75, 44.23 ppm. 1H NMR (D2O): 3.53 (8, 1 H), 3.18 (bs, 2 H), 3.06 (bs, 1 H), 2.90 ppm (bs, 1 H). Anal. Calcd for C12H24N40~ 2.5HC1: C, 37.98; H, 7.04; N, 14.76. Found: C, 37.87; H, 6.91; N, 14.61. 1,4,7-Triazacyclononane-N-met hanephosphonic Acid Dihydrochloride (16). Phosphorous acid (4.77 g, 58.2 mmol) was melted at 75 "C and 7 (1.418g, 2.34 mmol) was added in small portions while the temperature was maintained near 80 "C. After each addition, the brown solid dissolved and rapidly decolorized. Vapors evolved that were likely SOz, HzS, and 12. Five minutes after the final addition, 15 mL of ether was added. The product that precipitated was filtered, washed with 5 mL of ether, redissolved into 6 mL water, and purified on a Dowex 50x8 ion-exchange column (bed volume, 14 mL). The fractions containing product were lyophilized to give a white hydroscopic solid. The yield of 16 as a dihydrochloride salt was 21% (0.145 g, 0.48 mmol). lH NMR (D2O): 3.63 (8, 2 H), 3.32 (t,2 H, 3 J = 6.1 Hz), 3.11 (t, 2 H, 3 5 = 6.1 Hz), 3.01 ppm (d, 1 H, 2 J ~ =p 8.6 Hz). Ethyl Ethylphosphonite (17). Dichloroethylphosphine (Caution: Reacts explosively with water ut 25 "C) (19.3 g, 0.15 mmol) was added dropwise to 40 mL of absolute ethanol and 11.9 mL of pyridine at 0 "C within 30 min. The reaction mixture was stirred for an additional 30 min at 25 "C. The pyridine hydrochloride salt that is formed is filtered off prior to distillation of the product under reduced pressure (75-78 "C, 15 mmHg). The product was obtained in 80% yield (14.8 g, 0.12 mol). lH p 527 Hz), 4.11 (m, 2 NMR (CDC13): 7.06 (d, 1 H, 1 J ~ = H), 1.78 (m, 2 H), 1.37 (t, 3 H), 1.16 ppm (dt, 3 H, 3 J ~ p = 20 Hz).

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No. 6, lQQ2 531

(9, 4 H), 3.36 (bs, 6 H), 3.20 (bt, 4 H), 1.98 (m, 2 H), 1.35 (t,3 H), 1.14 ppm (dt, 3 H, 3 J= 18.3 ~ Hz). ~ Anal. Calcd

HI 25.16; -O. H,~5.50; ~ H N, ~ O8.00. : for C I ~ H ~ , ~ N ~ P O ~ - ~C, Found: C, 25.12; H, 5.35; N, 7.99. Ether (10 mL) was added to the filtrate, which gave another precipitate that was filtered off and was washed with ether. Yield: 0.167 g. This product contained about 10% [9laneN3 and 10% of another phosphorylated product, as evidenced by 'H NMR. 1,4,7-Triazacyclononane-N-methanep hosphonate Diethyl Ester (19). This compound was prepared using procedures described for 18, starting with 7 (0.341 g, 0.564 mmol) and 0.630 mL of diethyl phosphite. After 5 min, ethanol (1mL) was added to the reaction mixture and the product was precipitated from this solution by adding 3 mL of ether while stirring vigorously. The ethanol/water was decanted and the precipitate was washed with 5 mL of ether. The precipitate was dissolved in 1mL of ethanol and crystallized after 10 min. The crystals were filtered off and washed with ether. The precipitate was dissolved in water (5 mL). The pH of the water layer was adjusted to 13 by addition of NaOH. The product was extracted from the water layer with CHCl3 (50 mL). The latter CHC13 layer was dried with Na2S04 for several hours before evaporation in vacuum gave a colorless oil. Yield: 24% (0.034 g). 'H NMR (CDCl3): 4.08 (dt, 4 H), 2.97 (d, 'JHP = 8.5 Hz, 2 H), 2.73 (s, 4 H), 2.70 (s, 8 H), 2.35 (bs, 2 H, NH), 1.28 ppm (t, 3 J ~ p 7.3 Hz). 13C NMR (CDCl3): 61.71, 54.65, 52.28 (Vcp = 158 Hz), 46.99, 46.38, 16.52 PPm. 1,5,9-Triazacyclododecane-N-methanephosphonate Diethyl Ester (20). This compound was prepared as described for 19, starting with 8 (0.280 g, 0.441 mmol) and 0.625 mL of diethyl phosphite. The reaction was worked up by addition of 4 mL of ether giving a precipitate. The precipitate was washed with 2 X 4 mL of ether and then dissolved in 4 mL of ethanol. 1,5,9-Triazacyclododecane itself did not dissolve. The precipitate was removed by centrifugation. Ether (4 mL) was added to the clear ethanol solution and the product precipitated. The product was filtered off under nitrogen and was washed with ether (4 mL). The solid was extracted into CHC13. Yield: 31% (0.044 g). 1H NMR (CDCl3): 4.03 (dt, 4 H), 2.69 (m, 16 H), 1.57 (m, 6 H), 1.24 ppm (t,6 €3, 3 J ~ p 7.3 Hz). '3C NMR (CDCl3): 61.25, 53.36, 49.33, 47.19 ('Jcp = 150.9), 25.78, 25.66, 16.37 ppm. P-Ethyl 1,5,9-Triazacyclododecane-N-methanephosphinate Ethyl Ester (21). This compound was prepared as described for 20, starting with 8 (0.314 g, 0.495 mmol) and 0.625 mL of 17. Yield: 73% (0.111 g). 'H NMR (CDC13): 3.96 (dt, 2 H), 2.80 (bs, 2 H, NH), 2.63 (m, 14 H), 1.69 (m, 2 H), 1.55 (m, 6 H), 1.20 (t, 3 H), 1.04 ppm (dt, 3 H, 3 J ~ =p 17.7 Hz). 13CNMR (CDC13): 59.90,52.74, 50.49 (lJcp = 104 Hz), 48.63, 46.15, 25.72, 20.82 (Vcp = 87.9 Hz), 16.55, 5.65 ppm. 1,4,7,1O-Tetraazacyclododecane-N-methanephosphonic Acid Hydrochloride (22). Compound 5 was P-Ethyl1,4,7-Triazacyclononane-N-methanephos- prepared as described previously (1 mmol). After lyophilization, the resulting solid was added to 4 mL of 20% phinate Ethyl Ester Hydrochloride (18). Compound HC1 containing iodine (0.51 g, 2 mmol) and NaI (0.30 g, 7 (0.607 g, 1.00 mmol) was added to 1mL of 17 at 0 "C. 2 mmol). NaCl precipitated together with a brown gum. The resulting orange solution was warmed to room After 10 min, the solution was filtered over a cotton plug temperature and the reaction mixture turned yellow and and phosphorous acid (0.82 g, 10 mmol) was added. This gases evolved in about 1min. Ethanol (12 mL) was added solution was boiled for 3 h. The solution was evaporated and the solution was kept at 0 "C for several hours. The to dryness and coevaporated with 20 mL of water. The white crystals that formed were filtered and washed with solid was dissolved in 5 mL of water and purified on Dowex ethanol (0 "C) and ether (crystals turned light yellow 50x8 (bed volume, 40 mL). The product fraction was probably as a result of iodide oxidation by ether peroxides). evaporated under vacuum and lyophilized. The oily Yield: 43% (0.227 g). lH NMR (DzO): 4.15 (dt, 2 H), 3.65

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Bloconlugate Chem., Vol. 3, No. 8, 1992

material was treated with ether (10 mL) giving a white powder. Yield: 24% (0.103g). 'H NMR (D2O): 3.32 (bs, 4 H), 3.28 (bs, 8 H), 3.08 (be,4 H), 2.97 ppm (d, 2 H, 2 J ~ p = 9 . 8 H ~ ) .13CNMR (D20/H20): 52.46,50.54,44.42,43.98 ppm. 3lP NMR (D20/H20): 22.92 ppm. Anal. Calcd for C B H ~ ~ N ~ O ~ P - ~ H C ~C, * O25.67; . ~ H ~H,O 6.70; : N, 13.30. Found: C, 25.57; H, 6.74; N, 13.77. ACKNOWLEDGMENT

This research was supported by grants from the Robert

A. Welch Foundation (AT-584) and the Meadows Foundation. LITERATURE CITED (1) Bunzli, J.-C. G. and Choppin, G. R., Eds. (1989) Lanthanide Probes in Life, Chemical, and Earth Sciences: Theory and Practice, Chapters 4 and 5, Elsevier, New York. (2) Desreux, J. F., Merciny, E., and Loncin, M. F. (1981) Nuclear magnetic resonance and potentiometric studies of the protonation scheme of two tetraazatetraacetic macrocycles. Znorg. Chem. 20,987-991. (3) Geraldes, C. F. G. C., Sherry, A. D., Marques, M. P. M., Alpoim, M. L., and Corks, S. J. (1991) Protonation scheme for some triaza macrocycles studied by potentiometry and NMR spectroscopy. Chem. SOC.Perkin Trans. 2 137-146. (4) Geraldes, C. F. G. C., Sherry, A. D., and Cacheris, W. P. (1989) Synthesis, protonation sequence, and NMR studies of polyazamacrocyclicmethylenephosphonates. Znorg. Chem. 28, 3336-3341. (5) Kimura, E., Sakonaka, A., Yatsunami, T., and Kodama, M. (1981) Macromonocyclic polyamines as specific receptors for tricarboxylate-cycle anions. J. Am. Chem. SOC.103, 30413045. (6) Zompa, L. J. (1978) Metal complexes of cyclic triamines 2: Stability and electronic spectra of nickel(II), copper(I1) and zinc(I1) complexes containing nine- through twelve-membered cyclic triamine ligands. Znorg. Chem. 17, 2531-2536. (7) Yang, R., and Zompa, L. J. (1976) Metal complexes of cyclic triamines 1: Complexes of 1,4,7-triazacyclononane([glane N3) with nickel(II), copper(I1)and zinc(I1). Znorg. Chem. 15,14991502. (8) Gilbert, E. E. (1965) Sulfonation and Related Reactions, Chapter 5, Interscience, New York. (9) Backer, H. J., and Mulder, H. (1933) Acyl derivatives of aminomethanesulfonic acid. Red. Trau. Chim. Pays-Bas 52, 454-468. (10) Reinking, K., Dehnel, E., and Labhardt, H. (1905) Chem. Ber. 38, 1069. (11) Bucherer, H., and Schwalbe, A. (1906) Chem. Ber. 39,2796. (12) Backer, H. J., and Mulder, H. (1934) Acetylation of some 1,l aminosulfonic acids and 1 , l hydrazinesulfonic acids. Recl. Trau. Chim. Pays-Bas 53, 1120-1127. (13) Neelakantan, L., and Hartung, W. H. (1959) alpha-aminoalkane sulfonic acids. J. Org. Chem. 24, 1943-1948. (14) Knoevenagel, E. (1904) Chem. Ber. 37, 4073. (15) Miller, W. v., and Plochl, J. (1892) Chem. Ber. 25, 2020.

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