Tetrahydrofuran → 3-Hydroxymethyl-5-methyl-2,3-dihydro-benzo[1,4]dioxine-6-carboxylic acid (1-naphthalen-1-yl-ethyl)-amide

Beteiligte Stoffe

Reaktionsschritte

To a round bottom flask equipped with magnetic stirring and a nitrogen inlet was added 3-hydroxymethyl-5-methyl-2,3-dihydrobenzo[1,4]dioxine-6-carboxylic acid (2.00 g, 8.92 mmol), THF (45 mL), (R)-(+)-1-(1-naphthyl)ethylamine (2.23 mL, 8.92 mmol), and finally 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) (1.53 g, 9.81 mmol). This mixture was stirred at room temperature for 36 hours. A few drops of water were added and the mixture stirred for 5 minutes. The reaction was diluted with ether and washed once with 1N HCl, once with saturated sodium bicarbonate(aq), once again with 1N HCl, dried over magnesium sulfate, filtered and evaporated to provide 3-hydroxymethyl-5-methyl-2,3-dihydro-benzo[1,4]dioxine-6-carboxylic acid (1-naphthalen-1-yl-ethyl)-amide. Crystals of acceptable purity for x-ray crystallography were obtained by subliming the material twice under vacuum at 60° C. This x-ray analysis established the regiochemistry and the absolute stereochemistry of the compounds as shown, since the configuration of the naphthylethylamine stereocenter is known and not subject to racemization under the conditions of synthesis. 1H-NMR (300 MHz, CD3COCD3) δ (ppm): 1.71 (d, 3H), 2.22 (s, 3H), 3.80 (m, 2H), 4.06 (m, 1H), 4.23 (m, 2H), 4.32 (m, 1H), 6.09 (m, 1H), 6.65 (d, 1H), 6.87 (d, 1H), 7.55 (m, 3H), 7.69 (m, 2H), 7.83 (d, 1H), 7.94 (d, 1H), 8.35 (d, 1H); TLC Rf=0.12 (1:1 ethyl acetate/hexane).

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