Synthesis and characterization of the 6-deaza derivative of coenzyme PQQ, methyl 4,5-dihydro-4,5-dioxobenz[g]indole-2-carboxylate

Intramolecular C—H Amination Reactions: Exploitation of the Rh2(II)‐Catalyzed Decomposition of Azidoacrylates.

“…Purification by flash chromatography (2:98 -30:70 EtOAc:hexanes) afforded the product as a white solid (0.016 g, 98%). The spectral data for 14 matched that reported by Ohshiro and co-workers: 18 8 The general procedure at 40 °C was followed using 0.053 g of vinyl azide 8 (0.219 mmol), 0.0066 mg of Rh 2 (pfb) 4 (0.006 mmol), and 0.200 mL of toluene. Purification by flash chromatography (5:95 EtOAc:hexanes) afforded the indole product as a white solid (0.043 g, 91%).…”

“…The spectral data for 13 matched that reported by Babushkina and co-workers: 17 Benzindole 14. 18 The general procedure at 60 °C was followed using 0.018 g of vinyl azide 7 (0.071 mmol), 0.0038 mg of Rh 2 (pfb) 4 (0.004 mmol), and 0.066 mL of toluene. Purification by flash chromatography (2:98 -30:70 EtOAc:hexanes) afforded the product as a white solid (0.016 g, 98%).…”

Synthesis, Physicochemical Properties, and Amine-Oxidation Reaction of Indolequinone Derivatives as Model Compounds of Novel Organic Cofactor TTQ of Amine Dehydrogenases

“…4,5-Quinone isomer 5 was also synthesized by basically the same strategy from 2-carbomethoxy-3,7-dimethyl-5-benzyloxyindole ( 20 ) that can be prepared from 2-methyl-4-benzyloxyaniline and methyl α-ethylacetoacetate according to the established procedure of a combination of a Jaap−Klingemann reaction and a Fischer indolization as in the case of the starting materials 12 and 16 . , Removal of the carbomethoxy group of 20 by hydrolysis and thermal decarboxylation gave indole derivative 22 , which was converted into the expected 4,5-quinone 5 by the catalytic hydrogenation and the following Fremy's salt oxidation (Scheme ).…”

“…Disappearance of the absorption in the visible region by the reduction of the quinone to the quinol form is a similar feature of all the compounds. Judging from the IR absorption of carbonyl stretching of the quinone (ν CdO ) around 1630 cm -1 and 1 H and 13 C NMR chemical shifts of 2-H, 5-H, 6-C, and 7-C, the electronic structure of the 6,7-indolequinone moiety of each 6,7-quinone is essentially the same in the ground state. The lower ν CdO values (by ca.…”

“…2-Carboxy-3-methyl-4-phenyl-7-methoxyindole (13). The starting indole derivative ( 12 ) was prepared from 4-methoxy-3-biphenylamine and methyl α-ethylacetoacetate according to the established procedure (combination of a Jaap−Klingemann reaction and a Fischer indolization). , Compound 12 (65.5 mg, 0.222 mmol) was treated in 1 N KOH aqueous CH 3 CN solution (7 mL, 1:1, v/v) at 80 °C for 1 h. Acidification of the reaction mixture to pH 3 with 1 N HCl gave a white precipitate that was isolated by centrifugation and dried in vacuo (94%): mp >300 °C; IR (KBr) 3424 (NH), 1658 cm -1 (CO); 1 H NMR (CDCl 3 ) δ 2.18 (3 H, s), 2.69 (1 H, br s), 4.01 (3 H, s), 6.76 (1 H, d, J = 7.8 Hz), 6.89 (1 H, d, J = 7.8 Hz), 7.39−7.47 (5 H, m), 9.04 (1 H, br s); HRMS (EI) m/z 281.1064 (M + ), calcd for C 17 H 15 O 3 N 281.1053…”