Ethylenediamine → (3R,4S,5R)-5-amino-3-(1-ethyl-propoxy)-4-methanesulfonyloxy-cyclohex-1-enecarboxylic acid ethyl ester

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Reaction Steps

To a stirred suspension of 9.23 g (20 mmol) (1R,5R,6S)-2-{[3-ethoxycarbonyl-5-(1-ethyl-propoxy)-6-hydroxy-cyclohex-3-enylimino]-methyl}-benzenesulfonic acid sodium salt and 3.50 ml (25 mmol) of triethylamine in 90 ml ethyl acetate was added 1.80 ml (23 mmol) methanesulfonyl chloride at to 0 to 5° C. The resulting brown-yellowish suspension was stirred at room temperature for 2 hours, treated with 2.70 ml (40 mmol) ethylenediamine and after 10 min with 90 ml of water. After stirring the 2-phase system vigorously for 1 hour the organic phase was separated and extracted with 100 ml water and 3 times with 100 ml aqueous 1M NaHCO3 solution, dried over Na2SO4, filtered and evaporated in a rotary evaporator at 48° C./4 mbar to dryness to yield 6.36 g (91%) of (3R,4S,5R)-5-amino-3-(1-ethyl-propoxy)-4-methanesulfonyloxy-cyclohex-1-enecarboxylic acid ethyl ester as an orange oil. An analytical sample of was obtained by column chromatography on silica gel using t-BuOMe containing 1% of 25% ammonia as the eluent. IR (film): 2966, 2936, 2878, 1711, 1653, 1463, 1351, 1246, 1172, 1068, 961 cm−1; MS (EI, 7o eV)): 350 (M+), 262, 224, 182, 166, 136 m/z.

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