Photo-induced crystallization with emission enhancement (PICEE)

A new photoactivation mechanism, photo-induced crystallization with emission enhancement, is developed based on an isoquinolinium salt with applications in mitochondria-targeting and photodynamic therapy.

Rhodium-Catalyzed Cascade Annulative Coupling of 3,5-Diarylisoxazoles with Alkynes

A rhodium-catalyzed cascade annulative coupling of 3,5-di­arylisoxazoles with three equivalents of an alkyne proceeds smoothly in the presence of a Cu(II) oxidant, where the sequential construction of isoquinoline and naphtho[1,8-bc]pyran frameworks connected by a biaryl linkage is achieved by a single operation. Most of the obtained polycyclic compounds exhibit visible fluorescence in both the solution and the solid state. The hexaphenylated isoquinoline-naphthopyran conjugate (R = Ph) as a representative product shows a green emission which can be turned off by making an isoquinolinium salt with an acid. The emission is also reversibly turned on by treatment with a base.

Activities of Naphthylisoquinoline Alkaloids and Synthetic Analogs against Leishmania major

ABSTRACT The current treatments for leishmaniasis are unsatisfactory due to their toxic side effects, high costs, and increasing problems with drug resistance. Thus, there is an urgent need for alternative drugs against leishmaniasis. Different approaches have been used to identify novel pharmacophores against Leishmania sp. parasites, and one strategy has been the analysis of naturally occurring plant-derived compounds, including naphthylisoquinoline alkaloids. In the present study, we examined the abilities of these alkaloids to inhibit the growth of Leishmania major promastigotes and evaluated their effects on macrophages, dendritic cells, and fibroblasts. Furthermore, we determined the efficacy of selected compounds in decreasing the infection rate of macrophages and regulating their production of cytokines and nitric oxide. Our results demonstrate that the naphthylisoquinoline alkaloids ancistrocladiniums A and B (compounds 10 and 11) and the synthetic isoquinolinium salt (compound 14) were effective against intracellular amastigotes in the low submicromolar range, while toxicity against mammalian cells was observed at concentrations that were significantly higher than those needed to impair parasite replication. The activities of compounds 11 and 14 were mainly directed against the amastigote stage of L. major. This effect was not associated with the stimulation of host macrophages to produce nitric oxide or secrete cytokines relevant for the leishmanicidal function. In conclusion, our data suggest that ancistrocladiniums A and B (compounds 10 and 11) and the synthetically prepared isoquinolinium salt (compound 14) are promising candidates to be considered as lead compounds for leishmanicidal drugs.

Glycosidase-catalyzed hydrolysis of 2-deoxyglucopyranosyl pyridinium salts: effect of the 2-OH group on binding and catalysis

Three 2-deoxy-α-D-glucopyranosyl pyridinium tetrafluoroborates were tested for their binding affinity to a range of α-glucosidases and α-mannosidases. The α-isoquinolinium salt (11) binds approximately 275-fold more tightly to yeast α-glucosidase than does the isomeric quinolinium salt (12). In addition, compound 11 binds to the yeast enzyme approximately two-fold tighter than the corresponding glucopyranosyl isoquinolinium salt (9). The (kcat/khyd) values for the yeast α-glucosidase-catalyzed reactions of 11 and 9 are 1.6 × 105 and 2.0 × 109, respectively, when compared to the spontaneous uncatalyzed reactions. Thus, the interaction of the 2-OH group in compound 9 with the yeast enzyme's active site generates a relative transition state stabilization of about 23.5 kJ mol-1. For both compounds 11 and 12, the observed rate accelerations for the yeast α-glucosidase-catalyzed hydrolysis, relative to the spontaneous reaction in solution, (kcat/khyd) are identical within experimental error.Key words: glycosidase, inhibitor, 2-deoxyglucose, pyridinium, catalysis.

Photosolvolysis of Bridgehead Quaternary Ammonium Salts. III. Synthesis of Some 3-Benzazecine, 1H-2,6-Benzoxazecine and 2H-3,6-Benzoxazecine Derivatives and a 2H-1,4-Oxazocine Derivative

Photosolvolysis of a mixture of cis - and trans-9,10-dimethoxy-5-methyl- 1,3,4,6,7,11b-hexahydro-2H-benzo[a] quinolizinium iodide (2) in methanol gave, after workup, a very low yield of 8,10,11-trimethoxy-3-methyl- 1,2,3,4,5,6,7,8-octahydro-3-benzazecine (3a). Similarly 1,10,11 trimethoxy-6-methyl-3,4,5,6,7,8-hexahydro-1H-2,6-benzoxazecine (8a) and 1,10,11-trimethoxy-6-methyl-1,4,5,6,7,8-hexahydro-2H-3,6-benzoxazecine (16a) were obtained in fair and low yields respectively from the N- methyl tetrahydro-2H,6H-[1,3] oxazino [2,3-a] isoquinolinium (7a) and hexahydro [1,4] oxazino [3,4-a] isoquinolinium (15) iodide precursors; a 1- methyl derivative (8b) of (8a) was also prepared. The ring-opened products 3-[N-2-{(4,5-dimethoxy-2-dimethoxymethyl)-phenyl}ethyl-N-methyl]aminopropan-1-ol (9a) and 3-[N-2-{(4,5-dimethoxy-2-1′,1′- dimethoxyethyl )-phenyl}ethyl-N-methyl]aminopropan-1-ol (9b) were also obtained from the [1,3] oxazino [2,3-a]- isoquinolinium salt derivatives. Photolysis of (2) and 9,10-dimethoxy-5-methyl-1,3,4,6,7,11b-hexa-hydro[1,4] oxazino [3,4-a] isoquinolinium iodide (15) in acidified aqueous solution afforded, after workup, the benzazecin-8-ol (3b) and hexahydro-2H-3,6-benzoxazecin-1-ol (16b) products respectively, but again in very low yield. Some mechanistic rationalizations of these results are given.Photosolvolysis of 7a-(3,4-dimethoxy)phenyl-4-methyl-2,3,5,6,7,7a- hexahydropyrrolo [2,1-b] oxa-zolium iodide (22) in methanol afforded a high yield of 8-methoxy-4-methyl-8-(3,4-dimethoxy)-phenyl-3,4,5,6,7,8- hexahydro-2H-1,4-oxazocine (24) in a new ring-destruction approach to this ring system. From 13C n.m.r . data, the twist-boat-chair conformation was tentatively assigned to (24) in (D)chloroform solution.