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Antioxidant activities of 3-oxygenated and 3,4-dioxygenated carbazole alkaloids and their related carbazoles were comprehensively evaluated. In all assay systems, the 3,8-dihydroxycarbazoles carbazomadurin A (2) and B (3), and their synthetic precursors 2a and 3a exhibited higher antioxidant activities than the 3-monohydroxycarbazoles carazostatin (1), and the synthetic precursors 4a and 4b of carquinostatin A (4). In particular, 2a and 3a exhibited strong scavenging activities due to the reducing ability of formyl group at the C-5 position of carbazoles. The results suggest that these compounds could serve as useful clues for designing and developing novel antioxidants.

The total syntheses of the neuronal cell-protecting carbazole alkaloids carbazomadurin A and (S)-(+)-carbazomadurin B were achieved. The key step of the synthesis of the polysubstituted carbazole rings included an allene-mediated electrocyclic reaction of the 6π-electron system that involved the indole 2,3-bond. The cleavage of the alkoxy groups of the resulting 3-ethoxy-8-isopropoxycarbazole successfully gave the 3,8-dihydroxycarbazole, which was converted into the 3,8-bis(OSEM)-carbazole (SEM = 2-trimethylsilylethoxymethyl). A Suzuki–Miyaura cross-coupling reaction of the 3,8-bis(OSEM)-carbazole with the corresponding alkenyl pinacol borates afforded the 1-alkenylcarbazoles, which were treated with tetra-n-butylammonium fluoride (TBAF) followed by reduction with NaBH4 to provide carbazomadurin A and (S)-(+)-carbazomadurin B, respectively.

A new total synthesis of the neuronal cell-protecting carbazole alkaloid carbazomadurin A is described. The key step was an allene-mediated electrocyclic reaction involving an indole [b]-bond for the construction of a highly substituted carbazole ring. The E-alkenyl side chain at the C1 position of carbazole was introduced between O-triflate and alkenyl pinacol borate using the Suzuki–Miyaura reaction. SEM groups were cleaved with TBAF and the formyl group was reduced to provide carbazomadurin A.

A new bis-zinc(II) receptor (Zn2L), which has two macrocyclic 12-membered tetraamine (cyclen) ZnII complexes connected through a p-xylene bridge, has been synthesized as a novel host molecule to recognize barbiturates (such as barbital (bar)) in aqueous solution. Each of the zinc(II) ions in the biszinc(II) receptor was originally intended to match the dianionic barbital anion (bar2−) with supplementary hydrogen bonds between the cyclen NH's and the three carbonyl oxygens in complementary positions to yield a 1:1 complex, Zn2L–bar2−. From an aqueous solution of equimolar Zn2L and barbital at pH 8, however, a cyclic 2:2 complex, (Zn2L-bar2−)2, was isolated and characterized by X-ray crystal analysis. The NMR study in 10% (v/v) D2O/H2O has revealed dissociation of (Zn2L–bar2−)2 solely into the original target 1:1 complex Zn2L–bar2− and established the dimerization constant for 2Zn2L–bar2− → (Zn2L–bar2−)2, Kd ( = [(Zn2L–bar2−)2]/[Zn2L–bar2−]2) to be 103.4 M−1. The thermodynamic parameters were evaluated from the NMR measurements at 25, 35, 45, and 55°C: ΔG = –1.9 × 104 J mol−1, ΔH = – 3.3 × 104 J mol−1, ΔS = – 49 J mol−1 K−1 at 25°C. Potentiometric pH titration of Zn2L (1 mM) and barbital (1 mM) disclosed extremely facile deprotonation of the two imido groups of barbital at pH less than 7 to form the dianionic barbital-bound ZnII complexes Zn2L–bar2− and (Zn2L–bar2−)2, where-by the barbital binding affinity for Zn2L was estimated to be Kbar ( = [Zn2L–bar2−]/[uncomplexed Zn2L][uncomplexed barbital]) = 105.8 M−1 at pH 8 and 25°C with I = 0.10 (NaNO3). The significance of the bis-zinc(II) receptor in stabilizing the dianionic barbital is evident by comparison with the interaction of ZnII–cyclen complex (ZnL) with barbital, which yields only a 1:1 monoanionic barbital complex, ZnL–bar− (Kbar = [ZnL–bar−]/[uncomplexed ZnL][uncomplexed barbital] = 104.2M−1 at pH 8 and 25°C with I = 0.10 (NaNO3)).

Formation de complexe stable avec le citrate (3−), l'AMP (2−), l'ATP (4−), HPO 4 2− , [Fe(CN) 6 ] 4− et [Fe(CN) 6 ] 3−

A new synthesis of the 1-oxygenated 1,3-disubstituted carbazole alkaloids, mukonine (la) and clausine (If) is described. The construction of the carbazole framework is based on an allene-mediated electrocyclic reaction involving the indole 2,3-bond. The 1,3-disubstituted 1-oxygenated carbazoles la and If are derived from the 1,2,3-trisubstituted carbazole.

We synthesized 6-methylindole-4,5-quinone (1b) in order to clarify the structure of natural product, 5-methylindole-4,5-quinone (la) isolated from Drupella fragum. The synthesis features the construction of the indole ring based on an electrocyclic reaction of a 3-alkenyl-2-propargylpyrrole intermediate. Two synthetic methylindolequinones and their related compounds were examined in human lung cancer cell line NCI-H460 and human breast cancer cell line MDA-MB-231.

New macrocyclic polyamines L2–L5 have been synthesized to develop sequestering agents selective for Na+, K+, Mg2+ and Ca2+ ions in aqueous solutions. 18-membered hexadentate ligands L2 and L3 show specificity toward Ca2+, whereas a 16-membered pentaamine with an amine branch (L4) bind only to Mg2+.