Oxidation of 1-(3,4-Dimethoxyphenethyl)-3-ethyl-4-(carboxaldehyde diethylacetal)pyridinium Bromide by Potassium Ferricyanide

Bioinspired Syntheses of the Pyridoacridine Marine Alkaloids Demethyldeoxyamphimedine, Deoxyamphimedine, and Amphimedine

“…Using general procedure E, N-ethyl-styelsamine D (23, 11.5 mg, 0.02 mmol), paraformaldehyde (4.1 mg, 0.14 mmol), and acetic acid (2 mL) afforded 25 as a dark yellow powder (TFA salt, 7.61 mg, 83% yield). R t = 8.28 min; IR (ATR) ν max 3401, 1671, 1427, 1183, 1110, 1032 cm −1 ; 1 H NMR (CD 3 OD, 500 MHz) δ 9.95 (1H, s, H-9), 9.46 (1H, d, J = 5.5 Hz, H-12), 9.39 (1H, d, J = 5.5 Hz, H-11), 9.31 (1H, d, J = 4.9 Hz, H-6), 9.10 (1H, d, J = 4.9 Hz, H-5), 8.94 (1H, d, J = 8.0 Hz, H-4), 8.49 (1H, d, J = 8.0 Hz, H-1), 8.12 (1H, t, J = 8.0 Hz, H-2), 8.04 (1H, t, J = 8.0 Hz, H-3), 4.94 (2H, q, J = 7.2 Hz, H 2 -14), 1.82 (3H, t, J = 7.2 Hz, H 3 -15); 13 N-Benzyl-demethyldeoxyamphimedine (26). Using general procedure E, N-benzyl-styelsamine D (24, 8.1 mg, 0.02 mmol), paraformaldehyde (2.5 mg, 0.08 mmol), and acetic acid (1.5 mL) afforded 26 as a dark yellow powder (TFA salt, 6.04 mg, 74%).…”

“…We were interested in not only achieving oxidation but also discerning whether one or both of amphimedine ( 1 ) or neoamphimedine ( 2 ) were the product(s). The reagent of choice for oxidation of a methylpyridinium to an N -methylpyridone is K 3 [Fe­(CN) 6 ] in aq NaOH. ,, In the present study, oxidation of deoxyamphimedine 3 using alkaline ferricyanide yielded exclusively amphimedine ( 1 ) in 92% yield. A range of other oxidants were subsequently explored (data not shown), and it was found that the reaction of deoxyamphimedine ( 3 ) in DMSO/conc.…”