反应详情

A mixture of diethyl 2-amino-2-methylnonanedioate (2.73 g) with oct-1-en-3-one (1.323 g) was set aside at room temperature overnight. The resulting diethyl 2-methyl-2-((3-oxooctyl)amino)nonanedioate was taken up in ethanol (40 ml), treated with sodium borohydride (0.38 g) and stirred at room temperature for 21/2 hours. The ethanol was evaporated in vacuo, the residue was shaken with water and ether, and the ethereal solution was washed with water and dried over magnesium sulphate. Removal of the ether left diethyl 2-((3-hydroxyoctyl)amino)-2-methylnonanedioate as an oil (4.14 g) which was taken up in ethanol (20 ml), cooled in ice-water, and treated with 2 N-hydrochloric acid (10 ml) followed by potassium cyanate (1.62 g) in water (5.5 ml). The cooling bath was removed and the mixture was stirred overnight at room temperature; the ethanol was evaporated in vacuo, water (75 ml) was added, and the resulting gum was extracted into ether (75 ml). The ethereal solution was washed with water, dried over magnesium sulphate, and evaporated, and the residual oil was heated on the steambath for 6 hours, to give crude 5-(6-ethoxycarbonylhexyl)-1-(3-hydroxyoctyl)-5-methylhydantoin as a yellow-brown oil. The latter was stirred in water (20 ml) with 2 N-aqueous sodium hydroxide (10 ml) for 2 hours, residual oil was removed with ether, and the aqueous solution was acidified to Congo Red with hydrochloric acid. The liberated carboxylic acid was taken into ether and the ethereal solution was washed with water and dried over magnesium sulphate; removal of the ether left an oil (2.44 g) which was purified by chromatography on silica in 30:1 chloroform-methanol yielding 5-(6-carboxyhexyl)-1-(3-hydroxyoctyl)-5-methylhydantoin as a mixture of diastereomers. Separation by means of high-performance liquid chromatography (20-44μ Biosil, chloroform-methanol-acetic acid 97:1:5:1.5) afforded the individual racemic diastereomers as colourless gums, the less polar isomer having Rf. 0.47 relative to Rf. 0.43 for the more polar isomer on SiO2 in chloroform-methanol-acetic acid 90:5:5. The less polar isomer gave characteristic 'H n.m.r. signals at δ9.30 (1H, broad singlet, exch., NH), 6.22 (2H, broad singlet, exch., CO2H and OH), 3.6 (2H, multiplet, C-15 methine and one C-13 proton), 3.0 (1H, multiplet, one C-13 proton), 2.31 (2H, triplet, CH2 adjacent to CO2H), 1.40 (singlet, isolated CH3) and 0.87 (3H, triplet, terminal CH3) in CDCl3. The more polar isomer gave characteristic 'H n.m.r. signals at δ9.08 (1H, broad singlet, exch., NH), 5.41 (2H, broad singlet, exch. CO2H and OH), 3.6 (1H, multiplet, C-15 methine), 3.3 (2H, multiplet, C-13 protons), 2.32 (2H, triplet, CH2 adjacent to CO2H), 1.41 (singlet, isolated CH3) and 0.88 (3H, triplet, terminal CH3) in CDCl3.

1. customThe ethanol was evaporated in vacuo
2. stirringthe residue was shaken with water and ether
3. washthe ethereal solution was washed with water
4. dry with materialdried over magnesium sulphate
5. customRemoval of the ether
6. waitleft diethyl 2-((3-hydroxyoctyl)amino)-2-methylnonanedioate as an oil (4.14 g) which
7. temperaturecooled in ice-water
8. additiontreated with 2 N-hydrochloric acid (10 ml)
9. customThe cooling bath was removed
10. stirringthe mixture was stirred overnight at room temperature
11. customthe ethanol was evaporated in vacuo, water (75 ml)
12. additionwas added
13. extractionthe resulting gum was extracted into ether (75 ml)
14. washThe ethereal solution was washed with water
15. dry with materialdried over magnesium sulphate
16. customevaporated
17. temperaturethe residual oil was heated on the steambath for 6 hours