Acetic Anhydride → 3,5-Dioxohexanoic acid

Participants

Reaction Steps

Bis-Acetoxy Eleutherobin (2800) and Methyl-Ketal Precursors of Eleuthosides A and B (2900+3000) as illustrated in FIG. 27. To a solution of natural eleutherobin (4) (10.0 mg, 0.015 mmol, 1.0 equivalent), Et3N (6.0 mL, 0.043 mmol, 3.0 equivalents), and 4-DMAP (0.40 mg, 0.0033 mmol, 0.2 equivalents) in CH2Cl2 (0.60 mL) at 0° C. was added Ac2O (1.0 M in CH2Cl2, 0.017 mL, 0.017 mmol, 1.1 equivalents) and the reaction was stirred at the same temperature for 1 hour. The reaction mixture was then quenched by addition of saturated NaHCO3 solution (0.50 mL) and extracted with CH2Cl2 (5×20 mL). The combined organic extracts were dried over Na2SO4 and concentrated to provide a crude residue which was was purified by flash chromatography (silica gel, 2% MeOH in CH2Cl2) to afford triacetate 2800 (1.8 mg, 16%) along with an inseperable mixture of eleuthosides 2900 and 3000 (7.8 mg, 73%) as well as recovered 1 (0.5 mg, 5%). 2800. Rf=0.44 (silica gel, MeOH-- CH'2Cl2,1:20); [α]D -67.3 (c 1.2, CHCl3); FT-IR (neat) nmax 2962, 1746, 1740, 1644, 1634, 1372, 1226, 1156, 1068, 759, 668, 617 cm-1.

Provenance & Evidence