Synthesis of 4-alkoxy-Δ3-pyrrolin-2-ones and tetramic acids

Synthesis and Anti-Cancer Activity of C-Ring-Functionalized Prodigiosin Analogues

“…Drying over anhydrous MgSO 4 , followed by filtration, removal of the solvent under reduced pressure, and purification using flash chromatography on silica with a gradient of ethyl acetate:hexane (0:100-30:70) as eluent, gave the title compound as a white solid (2.9 g, 68%); mp ) 115 °C; R f 0.39 (50:50 ethyl acetate:hexane); δ H (500 MHz, CDCl 3 ) 10.29 (1H, bs), 9.64 (1H, s), 4.17 (2H, q, J 7.1), 3.07 (2H, t, J 6.5), 2.72 (2H, t, J 6.5), 2.61 (3H, s), 2.60 (3H, s), 1.27 (3H, t, J 7.1); δ C (125 MHz, CDCl 3 ) 195.0, 177. Ethyl 6-(5-Formyl-2,4-dimethyl-1H-pyrrol-3-yl)-6-oxohexanoate (37). Following the procedure as for the synthesis of 36, the title compound was obtained as a white solid (34%); mp ) 83 °C; R f 0.55 (50:50 ethyl acetate:hexane); δ H (500 MHz, CDCl 3 ) 9.84 (1H, bs), 9.65 (1H, s), 4.13 (2H, q, J 7.1), 2.76 (2H, t, J 6.8), 2.58 (3H, s), 2.57 (3H, s), 2.36 (2H, t, J 7.0), 1.76-1.69 (4H, m), 1.25 (3H, t, J 7.1); δ C (125 MHz, CDCl 3 ) 197.0, 177.5, 173.…”

Naturally Occurring Tetramic Acids: Structure, Isolation, and Synthesis

“…TosNHNa; (b) NaOMe, 65'; (c) NaOH this strategy shows promise as a viable entry to tetramic acid natural products.A number of other synthetic routes to simple pyrrolidine-2,4-diones have been published over the years, namely: base-induced rearrangement of spiro p-lactams 168,177 intramolecular thermal rearrangement of 6-(aminoalkyl)-1,3-diox-5-en-4-ones169,178 fluoride ion-promoted cyclization of 4-bromobutanamides 170,179 ring opening of Meldrum's acid derivatives 171 by aminoacetonitrile,ls0 intramolecular Wittig reaction of y-acylphosphonium ylides 172,1E1 radical cyclization of propargyl bromoamides 173,lS2 cyclization of y-amino-P-keto esters 174,1a3 and finally…”

Five‐Membered Heterocycles: Pyrrole and Related Systems

“…The methyl tetramate 403, as well as several similar compounds, is available by treatment of methyl 4-bromo-3-methoxy-2-butenoate 404 with methylamine [634], and may be converted into the corresponding 3-alkoxypyrroles, for instance 405, by treatment with diisobutylaluminium hydride (Scheme 4.125) [617]. Furthermore, the representative tetramate 403 undergoes metallation at C5 upon exposure to butyllithium, and the resulting lithio derivative gives access to various C5 substituted products after subsequent treatment with suitable electrophiles [635].…”