[OH-].[Na+].[O:3]=[C:4]1[C:17]2[CH:16]=[C:15]([O:18][CH2:19][CH2:20][CH2:21][CH2:22][C:23]([OH:25])=[O:24])[CH:14]=[CH:13][C:12]=2[O:11][C:10]2[C:5]1=[CH:6][CH:7]=[CH:8][CH:9]=2.[BH4-].[Na+].C(O)(C(F)(F)F)=O.C(Cl)Cl>O.CC(C)=O>[OH:3][CH:4]1[C:17]2[CH:16]=[C:15]([O:18][CH2:19][CH2:20][CH2:21][CH2:22][C:23]([OH:25])=[O:24])[CH:14]=[CH:13][C:12]=2[O:11][C:10]2[C:5]1=[CH:6][CH:7]=[CH:8][CH:9]=2Aqueous 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##
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