Tetraazacyclododecan

CO3 species was formed and the X-ray structure solved. It is thought that the carbonate species forms on reaction with water, which was problematic in the selected strategy, as water was produced in the formation of the dialkyl carbonates. Other problems included compound solubility and the stability of the monoalkyl carbonate complex. Van Eldik and co-workers also carried out a detailed kinetic study of the hydration of carbon dioxide and the dehydration of bicarbonate both in the presence and absence of the zinc complex of 1,5,9-triazacyclododecane (12[ane]N3). The zinc hydroxo form is shown to catalyze the hydration reaction and only the aquo complex catalyzes the dehydration of bicarbonate. Kinetic data including second order rate constants were discussed in reference to other model systems and the enzyme carbonic anhy-drase.459 The zinc complex of the tetraamine 1,4,7,10-tetraazacyclododecane (cyclen) was also studied as a catalyst for these reactions in aqueous solution and comparison of activity suggests formation of a bidentate bicarbonate intermediate inhibits the catalytic activity. Van Eldik concludes that a unidentate bicarbonate intermediate is most likely to the active species in the enzyme carbonic anhydrase.460... 

Tri- and tetraaza macrocycles A-functionalized with imidazole and pyrazole groups have been coordinated to zinc. The zinc complexes of functionalized 1,5,9-trizacyclododecane and 1,4,8, 11-tetraazacyclododecane have been synthesized, (76) and (77).680-685 The formation constants with the mono-armed 1,5,9-triazacyclododecane were calculated and found to be higher than for the non-functionalized macrocycle and coordination was demonstrated to be through four nitrogen... 

Weisman and Reed have developed a route to cyclen (1,4,7,10-tetraazacyclododecane) via a fused 5 6 5 tricyclic system which was formed from condensation of triethylenetetramine 383 and dithiooxamide 381 to give 2,3>5,6,8,9-hexahydrodiimidazo[l,2- 2, l -c]pyrazine 382 in 69% yield (Scheme 30) <1996JOC5186>. 

Macke recently introduced a monoreactive DOTA prochelator (4,7,10-tricarboxymethyl-tert-butyl ester A, A, A", A "-tetraazacyclododecane-1 -acetate), which was coupled to Tyr3—Lys5 (BOQ-octreotide via solid-phase peptide synthesis. A one-step deprotection reaction generated the bioactive compound DOTATOC in about 65% yield.142 The 90Y and 177Lu DOTATOC complexes have shown promise for the treatment of neuroendocrine tumors in early clinical trials.143,444... 

After our report, many other examples of SIMs based on mononuclear lanthanide complexes have appeared. As relevant examples, we should mention the erbium-organometallic double-decker complexes [11] and the dysprosium-acetylacetonate complexes [12], and the dysprosium-DOTA (H4DOTA, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) complexes reported by Sessoli etal. [13]. 

Renn, O., and Meares, C.F. (1992) Large scale synthesis of the bifunctional chelating agent 2-p-nitroben-zyl-l,4,7,10-tetraazacyclododecane-N,N, N"N" -tetraacetic acid and the determination of its enantiomeric purity by chiral chromatography. Bioconjugate Chem. 3, 563-569. 

While the basic and or applied chemistry of saturated macrocyclic polyamines, typically represented by 1,4,7,10-tetraazacyclododecane (cyclen, 1) and 1,4,8,11-tetraazacyclotetradecane (cyclam, 2), have both... 

The use of a lipophilic zinc(II) macrocycle complex, 1-hexadecyl-1,4,7,10-tetraazacyclododecane, to catalyze hydrolysis of lipophilic esters, both phosphate and carboxy (425), links this Section to the previous Section. Here, and in studies of the catalysis of hydrolysis of 4-nitrophenyl acetate by the Zn2+ and Co2+ complexes of tris(4,5-di-n-propyl-2 -imidazolyl)phosphine (426) and of a phosphate triester, a phos-phonate diester, and O-isopropyl methylfluorophosphonate (Sarin) by [Cu(A(A(A/,-trimethyl-A/,-tetradecylethylenediamine)l (427), various micellar effects have been brought into play. Catalysis of carboxylic ester hydrolysis is more effectively catalyzed by A"-methylimidazole-functionalized gold nanoparticles than by micellar catalysis (428). Other reports on mechanisms of metal-assisted carboxy ester hydrolyses deal with copper(II) (429), zinc(II) (430,431), and palladium(II) (432). 

Tetraaryltin compounds, 24 810-811 Tetraazacyclododecane derivatives, 24 56 Tetraazaindoles, as chemical stabilizers, 19 365... 

A particular ring expansion corresponding to a tetramerization of 1-benzylaziridine may be induced anod-ically leading to a tetraazacyclododecane (Scheme 131) [241]. 

Fig. 10. (A) Structure and (B) fluorescence emission spectrum of Tb-[N-2-pyridylmethyl)-N, N",N" -tris(methylenephosphonic acid butyl ester)-l,4,7,10-tetraazacyclododecane] (Tb-PCTMB). Reprinted with permission from [126], Copyright 1999 American Chemical Society...

The potentially octadentate, pendant arm ligand l,4,7,10-tetrakis(pyrazol-l-ylmethyl)-l,4,7,10-tetraazacyclododecane (L (182)) gives [MnL][PF6]2 Me2CO with manganese(II)." The crystal structure of this complex shows that the central metal is coordinated by eight nitrogens of L. 

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