ethyl 2-methyl-1-oxido-3,4-dihydropyrrol-1-ium-2-carboxylate

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: AMPO was prepared from EMPO based on the procedure described previously with minor modification.2 A solution of 0.5 g of EMPO was mixed with 10 mL of concentrated ammonium hydroxide in a sealed tube for 5 days at room temperature with shaking. The mixture was rotary evaporated to yield a viscous dark oil and passed through a silica gel column (200-400 mesh 60 Å) twice using methanol-ethyl acetate (30:70) as solvent. White crystalline product was obtained (0.10 g, 24%), mp. 134-135° C. (lit. 137° C.)., (corrected using 3,4 dimethoxybenzoic acid, m.p., 180° C. and urea, m.p., 135° C.). 1H NMR (400 MHz, D2O) δ 1.64 (3 H, s, C(5)Me), 2.21-2.29 and 2.54-2.61 (2 H, m, C(4)H), 2.73-2.73 (2 H, m, C(3)H), 7.36 (1 H, t, C(2)H). 1H NMR (400 MHz, CDCl3) 1.90 (3 H, s, C(5)Me), 2.27-2.34 and 3.14-3.20 (2 H, m, C(4)H), 2.79 (2 H, m, C(3)H), 7.19 (1 H, t, C(2)H), 5.85 and 8.46 (2 H, br, NH2). 13C NMR (100 MHz, CDCl3) δ 24.2 (s, —CH3), 25.0 (s, C-3), 30.5 (s, C-4), 79.1 (C-5), 137.4 (C-2), 172.9 (—C═O). IR (Neat film) 1676 (C═O), 1585 (C═N), 1215 (N—O). ESI-MS calcd for C6H10N2O2Na+ m/z 165.0634, found 165.0637 amu. Anal. Calcd. for C6H10N2O2: C, 50.81; H, 7.23; N, 19.14. Found: C, 50.61; H, 7.25; N, 19.31. The mixture was rotary evaporated to yield a viscous dark oil White crystalline product was obtained (0.10 g, 24%), mp. 134-135° C. (lit. 137° C.)

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: The nitrone 5-carbamoyl-5-methyl-1-pyrroline N-oxide (AMPO) was successfully synthesized and characterized. Spin trapping by AMPO of hydroxyl, superoxide, C-centered, sulfite, and tert-butoxyl radicals has been demonstrated for the first time by electron paramagnetic resonance (EPR) spectroscopy. Resulting spin adducts for each of these radicals gave unique spectral profiles. Rate of superoxide radical trapping was obtained by competitive trapping by AMPO versus DEPMPO and gave kAMPO=38 M−1 s−1 (based on kDEPMPO=58 M−1 s−1) comparable to that of EMPO kEMPO=44 M−1 s−1. The half-life of AMPO-O2 adduct is about t1/2˜10 minutes similar to that observed from EMPO but significantly shorter than that of DEPMPO-O2 adduct t1/2˜16 minutes. Theoretical analyses using density functional theory calculations at the B3LYP/6-31=G**/B3LYP6-31G* level were performed on AMPO and its corresponding suproxide product. Calculations predicted the presence of intramolecular H-bonding in both AMPO and its superoxide adduct, and these interactions were further confirmed by an X-ray structure (in the case of AMPO) of a novel and the amido nitrone compound 2-amino-5-carbamoyl-5-methyl-1-pyrroline N-oxide (NH2-AMPO). The thermodynamic quantities for superoxide radical trapping by various nitrones have been found to predict favorable formation of certain isomers. The measured partition coefficient in an n-octanol/buffer system of AMPO gave a comparable value to those of DMPO and DEPMPO. This study demonstrates the suitability of AMPO nitrone as spin trap to study radical production in aqueous systems. 2˜10 minutes 2˜16 minutes The measured partition coefficient in an n-octanol/buffer system of AMPO