Dichloromethane → 1,2,3,3a,8,8a-Hexahydro-alpha-oxo-1,3a,8-trimethyl-5-pyrrolo[2,3-b]indole acetic acid, phenylethyl ester

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Reaction Steps

To a chilled (0° C.) solution of 1,2,3,3a,8,8a-hexahydro-α-oxo-1,3a,8-trimethyl-5-pyrrolo[2,3-b]indole acetic acid, ethyl ester (0.76 g) in anhydrous phenylethyl alcohol (18.1 ml) was added titanium (IV) ethoxide (0.22 ml) via syringe under a nitrogen atmosphere. The solution was warmed to room temperature and heated to just under reflux for 3 hours. The solution was then cooled to 0° C. and saturated NH4Cl solution was added slowly until a precipitate formed. Methylene chloride (200 ml) was then added and the mixture extracted twice with 100 ml portions of saturated aqueous NH4Cl solution, twice with 100 ml of saturated aqueous NaHCO3 and once with 100 ml of brine. The organic extracts were dried (Na2SO4), filtered, and the solvent removed on the rotary evaporator. The phenylethyl alcohol was then removed by distillation under high vacuum. The resulting residue was purified using preparative HPLC (silica gel, 4% methanol in ethyl acetate as the loading solvent and eluent). The appropriate fractions were combined, and the solvent removed to yield 0.72 g of 1,2,3,3a,8,8a-hexahydro-α-oxo-1,3a,8-trimethyl-5-pyrrolo[2,3-b]indole acetic acid, phenylethyl ester, as an oil.

Provenance & Evidence