Drx 400 nmr

OA derivatives were synthesized according to a previously described method [22 (link)]. To obtain the methyl ester (Me-OA) (compound 2 in Fig 1), a 40% (m/v) aqueous solution of KOH (7.5 mL, 0.1 mM) was added to diethyl ether (40 mL) followed by addition of 2 g (0.02 M) of nitrosomethylurea at 0°C. The yellow ethereal layer of diazomethane (CH₂N₂) was poured into the tetrahydrofuran (THF) (5 mL, 0.07 mM) solution of OA (500 mg, 1.09 mmol). The mixture was left in a fume hood overnight and compound 2 was obtained as a whitish powder (65%) with m.p. 124–126°C. Compound 2 (1.20 g, 2.55 mmol) was then oxidized with iodoxybenzoic acid (IBX; 2.86 g, 10.2 mmol) in dimethyl sulphoxide (DMSO; 35 mL). This was followed by epoxidation of the oxidized product using m-chloroperoxybenzoic acid (mCPBA; 321 mg, 1.3 mM). The epoxidation product was then brominated with hydrobromic acid (44 μL, 0.38 mM) and bromine (0.12 mL, 1.04 mmol) in acetic acid (10 mL) to yield compound 3 (Fig 1) (30%). An analytically pure sample of this compound was obtained by column chromatography (hexanes-EA, 4:1 to 2:1) as a yellowish solid with m.p. 137–140°C. All structures of synthetic products were confirmed by ¹H, ¹³C NMR and infrared spectroscopy. Spectra were recorded on a Bruker DRX-400 NMR and a Bruker Alpha FT-IR spectrometer. The pure compounds were used for animal studies.