Sodium Hydroxide → Pentanoic acid, 5-[(9-hydroxy-9H-xanthen-2-yl)oxy]-

Participants

Reaction Conditions

Reaction Steps

Aqueous NaOH (9 mL, 1 N, 9 mmol) was added dropwise to adjust a solution of 5-(9-oxoxanthen-2-oxy)valeric acid (2.5 g, 8.0 mmol), prepared as described above, in water (60 mL) to a pH of 8. Sodium borohydride (2.5 g, 66 mmol) was added in small portions over 15 min. The mixture was stirred at 50° C. for 3 hours (TLC showed no starting ketone), and then acetone (60 mL) was added carefully to decompose excess sodium borohydride. The mixture was partially concentrated (to ~70 mL) in vacuo at 25° C., and the remaining aqueous solution added dropwise to a well-stirred mixture of ice-water (40 mL) and glacial acetic acid (30 mL). The immediate precipitate was collected, washed with water (3×20 mL) and anhydrous ether (2×20 ml) and dried in vacuo over P2O5 to give a white powder. Yield: 2.4 g(97%). There was a very small amount of by-product (Rf =0.02) in TLC; the main product Rf =0.51; [EtoAc-MeOH(2:1) major spot which became yellow after spraying with TFA-CH2Cl2 (1:19) at 25° C.], 0.02 minor impurity. NMR data in accordance with structure. ##STR11##

Provenance & Evidence