Synthesis, characterization, and crystal structure of the gadolinium(III) chelate of (1R,4R,7R)-[alpha],[alpha][prime],[alpha][double prime]-trimethyl-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3MA)
- Bristol-Myers Squibb Pharmaceutical Research Inst., New Brunswick, NJ (United States)
- Bristol-Myers Squibb Pharmaceutical Research Inst., Princeton, NJ (United States)
The tetraazatricarboxylic macrocycle, (1R,4R,7R)-[alpha],[alpha][prime],[alpha][double prime]-trimethyl-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3MA) (4) was synthesized by the simultaneous hydrogenolysis and deformylation of 10-formyl-1,4,7-tris(benzyloxycarbonylmethyl)-1,4,7,10-tetraazacyclododecane (N-CHO-DO3MA-TBE) (11). Chelation of DO3MA with gadolinium acetate resulted in a diastereomerically pure Gd(III) chelate, Gd(DO3MA) (4a). X-ray structure analysis of Gd(DO3MA) crystals revealed that the three asymmetric carbons bearing [alpha]-methyl groups all have the (R)-configuration and that the chelate crystallizes as a dimer, [(DO3MA)Gd][(DO3MA)Gd(H[sub 2]O)[sub 2]], in which both the Gd atoms are enneacoordinate. Crystal data are as follows: [2(GdC[sub 17]H[sub 29]N[sub 4]O[sub 6])[center dot]2H[sub 2]O][center dot]4H[sub 2]O, a = 17.471(6) [angstrom], b = 25.495(6) [angstrom], c = 10.146(3) [angstrom], V = 4520(4) [angstrom][sup 3], P2[sub 1]2[sub 1]2[sub 1], Z = 4, R = 0.035, R[sub w] = 0.044. The relaxivity of Gd(DO3MA) was found to be 4.4 [+-] 0.1 mM[sup [minus]1] s[sup [minus]1] at 20 MHz and 40[degrees]C. The measured stability constant of Gd(DO3MA) was log K[sub eq] = 25.3, which makes Gd(DO3MA) the most stable heptadentate chelate known for Gd(III). 28 refs., 3 figs., 4 tabs.
- OSTI ID:
- 5716901
- Journal Information:
- Inorganic Chemistry; (United States), Journal Name: Inorganic Chemistry; (United States) Vol. 32:13; ISSN 0020-1669; ISSN INOCAJ
- Country of Publication:
- United States
- Language:
- English
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