8-Benzenesulfonyloxy-5- N,N-dimethylaminosulfonylquinolin-2-ylmethyl-pendant cyclen (BS-caged-L(4), BS = benzenesulfonyl) was designed and synthesized as a "caged" derivative of a previously described Zn(2+) fluorophore, 8-hydroxy-5- N,N-dimethylaminosulfonylquinolin-2-ylmethyl-pendant cyclen (L(4)) (cyclen = 1,4,7,10-tetraazacyclododecane). In the absence of metal ions and in the dark, BS-caged-L(4) (10 microM) showed negligible fluorescence emission at pH 7.4 (10 mM HEPES with I = 0.1 (NaNO3)) and 25 degrees C (excitation at 328 nm). Addition of Zn(2+) induced an increase in the UV/vis absorption of BS-caged-L(4) (10 microM) at 258 nm and a significant increase in fluorescence emission at 512 nm. These responses are results from the formation of Zn(H-1L(4)) by the hydrolysis of the sulfonyl ester at the 8-position of the quinoline unit promoted by the Zn(2+)-bound HO(-). Improvement of cell membrane permeation in comparison with L(4) is also described.

We previously reported on a 8-quinolinol-pendant cyclen (L(5)) as a Zn(2+) fluorophore (cyclen = 1,4,7,10-tetraazacyclododecane) and its caged derivative, 8-(benzenesulfonyloxy)-5-(N,N-dimethylaminosulfonyl)quinolin-2-ylmethyl-pendant cyclen (BS-caged-L(5)), which can be reactivated by hydrolysis of benzenesulfonyl group upon complexation with Zn(2+) at neutral pH to give a 1:1 Zn(2+)-L(5) complex (Zn(H(-1)L(5))). We report herein on the synthesis of 5,7-bis(N,N-dimethylaminosulfonyl)-8-hydroxyquinolin-2-ylmethyl-pendant cyclen (L(6)) and its caged derivative (BS-caged-L(6)) for more sensitive and more efficient cell-membrane permeability than those of L(5) and BS-caged-L(5). By potentiometric pH, (1)H NMR, and UV-vis spectroscopic titrations, the deprotonation constants pK(a1)-pK(a6) of H(5)L(6) were determined to be <2, <2, <2, 2.5 +/- 0.1 (for the 8-OH group of the quinoline moiety), 9.7 +/- 0.1, and 10.8 +/- 0.1 at 25 degrees C with I = 0.1 (NaNO(3)). The results of (1)H NMR, potentiometric pH, UV-vis, and fluorescent titrations showed that L(6) rapidly forms a 1:1 complex with Zn(2+) (Zn(H(-1)L(6))), the dissociation constant of which is 50 fM at pH 7.4. The fluorescent emission of Zn(H(-1)L(6)) at 478 nm is 32 times as large as that of L(6) (excitation at 370 nm), and the fluorescent quantum yield of Zn(H(-1)L(6)) (Phi(F) = 0.41) is much greater than that of Zn(H(-1)L(5)) (Phi(F) = 0.044). The BS-caged-L(6) was reactivated by hydrolysis of the benzenesulfonyl moiety more rapidly (completes in 30 min at pH 7.4 at 37 degrees C) than BS-caged-L(5), presumably enabling the practical detection of Zn(2+) in sample solutions and living cells. The photochemical deprotection of BS-caged-L(6) and the cell membrane permeability of L(6) and BS-caged-L(6) are also described.

Photochemical cleavage reactions of 8-quinolinyl benzenesulfonate derivatives and related sulfonates in aqueous solutions are reported. The 8-quinolinyl benzenesulfonates undergo photolysis upon photoirradiation at 300-330 nm to give the corresponding 8-quinolinols and benzenesulfonic acids with the production of only negligible amounts of byproducts. The effects of substituent groups of the 8-quinolinyl moiety and the benzene ring on the photolysis reactions were examined. Based on steady-state mechanistic studies using a triplet sensitizer, a triplet quencher, and electron donors, it was suggested that the photolysis proceeds mainly via the homolytic cleavage of S-O bonds in the excited triplet state.

A 41-year-old woman was admitted due to a sudden-onset severe headache, left hemiparesis and dysarthria. Diffusion-weighted magnetic resonance imaging showed an acute infarct in the bilateral pons, and magnetic resonance angiography revealed basilar artery (BA) occlusion resulting from dissection of the right vertebral artery (VA). She was treated with intravenous recombinant tissue plasminogen activator (rt-PA) 110 minutes after symptom onset. Subsequently, brain angiography was performed along with mechanical thrombolysis using Trevo ProVue retriever devices. The BA was successfully recanalized 240 minutes after the onset of symptoms. Thrombectomy is a promising treatment strategy for cases of VA dissection resistant to intravenous rt-PA thrombolysis.