Beyerol, dihydro-, triacetate

An anthraquinone conjugated macrocyclic chelating agent, 2,2',2″-(10-(2-(9,10-dioxo-9,10-dihydroanthracen-1-ylamino)-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetic acid or DO3A-Act-AQ, was synthesized by reacting trisubstituted cyclen (DO3A) with 2-chloro-N-(9,10-dioxo-9,10-dihydro-anthracen-1-yl)-acetamide and radiolabeled with (68)GaCl3 in 84% efficiency and a specific activity of 4.62 MBq/nmol. The IC50 value for BMG-1 cells was 0.1 mM, while the same concentration of DO3A-Act-AQ rendered no significant toxicity in HEK cells. The exposure of BMG-1 cells with 0.1 mM DO3A-Act-AQ displayed a time-dependent increase in apoptosis (40.7% at 4 h and 53% at 24 h), and the effect was 2.8- and 3.6-fold % higher as seen in HEK cells. An increase in S-phase cell population suggested S-phase arrest concomitant with induction of apoptosis in BMG-1 cells reaching to 4.5 times after 24 h with respect to control cells. DNA binding studies on CT-DNA (calf thymus) revealed a quenching pattern in the presence of DO3A-Act-AQ (10-70 μM), and the Stern-Volmer quenching constant was 2.4157 × 10(6) L mol(-1), indicative of strong binding with ds-DNA. A decrease in the positive and negative bands of CT-DNA was seen at 278 nm and 240 nm, respectively, on addition of 0.05 mM of DO3A-Act-AQ in CD studies. (68)Ga-DO3A-Act-AQ was stable in vitro in both PBS and human serum for at least 2 h. The in vivo blood kinetics study performed on normal rabbits indicated fast clearance with t1/2(F) = 40 ± 0.3 min and t1/2(S) = 3 h 30 min ± 0.1 min. Ex vivo biodistribution analysis displayed a favorable tumor-to-muscle ratio of 8.4 after 2 h in athymic nude mice xenografted with BMG-1 cells, suggesting the specificity of (68)Ga-DO3A-Act-AQ toward tumors.

It was found by 1H, 13C and 15N NMR study that substitution of 4,9-dihydro-4,6-dimethyl-9-oxo-3-(2',3',5'-tri-O-acetyl-beta-D-ribofuranosyl) imidazo [1,2-a]purine (wyosine triacetate, 1) at C2 position with electronegative groups CH30 and C6H5CH2O results in a noticeable electron distribution disturbance in the "left-hand" imidazole ring and a significant increase in the North conformer population of the sugar moiety.

PhenHDO3A is a ditopic ligand featuring a tetraazacyclododecane unit substituted by three acetate arms and one 6-hydroxy-5,6-dihydro-1,10-phenanthroline group (PhenHDO3A = rel-10-[(5R,6R)-5,6-dihydro-6-hydroxy-1,10-phenantholin-5-yl)-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid). This ligand was specially designed so as to obtain highly stable heteropolymetallic assemblies. PhenHDO3A has been prepared starting from phenanthroline epoxide and either a triprotected tetraazacyclododecane or tert-butyl triester of N,N',N' '-tetraazacyclododecane-triacetic acid. The latter yields PhenHDO3A in a single step. PhenHDO3A forms kinetically stable lanthanide complexes (acid-catalyzed kinetic constant kH = (1.2 +/- 0.2) x 10(-3) s(-1) M(-1)) whose solution structure has been deduced from a quantitative analysis of the paramagnetic shifts and the longitudinal relaxation times of the proton nuclei of YbPhenHDO3A. The alcohol group of the dihydro-phenanthroline unit remains coordinated to the encapsulated metal ion despite the steric crowding brought about by this group. Furthermore, the complexes are monohydrated, as shown by luminescence lifetime measurements on EuPhenHDO3A solutions. Relaxivity titrations at 20 MHz clearly indicate that the phenanthroline unit of GdPhenHDO3A is available for the spontaneous formation of highly stable tris complexes with the Fe2+ and Ni2+ ions. The water-exchange times and the rotational correlation times of GdPhenHDO3A and Fe(GdPhenHDO3A)32+ have been deduced from variable temperature 17O NMR studies and from nuclear relaxation dispersion curves. Despite rather slow water-exchange rates (taum0 = 1.0-1.2 x 10(-6) s), relaxivity gains of 90% have been observed upon the formation of the heterometallic tris complexes. The latter rotate about four times more slowly (taur0= 398 ps) than the monomeric unit (taur0 = 105 ps) and their relaxivity is, accordingly, twice as high. The relaxivity of the tris complexes between 10 and 50 MHz is comparable to relaxivities reported for Gd3+-containing dendrimers of much higher molecular weights. The high relaxivity of the tris-PhenHDO3A lanthanide complexes is attributed to their internal rigidity.