Sodium Bicarbonate → (S)-2-[1-(9-fluorenylmethyloxycarbonyl)-6-oxo-1,7-diazaspiro[4.4]non-7-yl]propionic acid

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Reaction Steps

Excess solid sodium bicarbonate was added to (S)-2-(6-oxo-1,7-diazaspiro[4.4]non-7-yl)propionic acid (0.42 g) in water (2 ml) and then 9-fluorenylmethylsuccinimidyl carbonate (0.7 g) in acetone (3 ml) was added. The mixture was stirred for 18 hours. The mixture was then addled to water (10 ml), extracted with ether (10 ml) and the aqueous layer separated. (The ether extracts were discarded). The pH of the aqueous layer was adjusted to 3 with concentrated hydrochloric acid and then it was extracted with dichloromethane (2×10 ml). The combined extracts were separated, dried (MgSO4) and evaporated to give (S)-2-[1-(9-fluorenylmethyloxycarbonyl)-6-oxo-1,7-diazaspiro[4.4]non-7-yl]propionic acid (0.62 g) as a white foam; NMR (d6-DMSO (373K)): some doubling of peaks due to the mixture of diastereoisomers, 1.3 (2d, 3H), 1.6-2.0 (m, 6H), 3.05 (m, 1H), 3.2-3.45 (m, 3H), 4.2-4.4 (m, 1H), 4.5 (m, 1H), 6.2 (s, 2H), 7.35 (m, 4H), 7.8 (m, 4H).

Provenance & Evidence