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

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Reaction Steps

To a stirred 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 (3.0 g) in n-hexyl alcohol (73.6 ml) was added at 0° C. under a nitrogen atmosphere, titanium IV ethoxide (0.83 ml). The mixture was warmed to room temperature and heated for 2 hours keeping the temperature between 60°-80° C. The excess n-hexyl alcohol was removed by distillation under high vacuum. The residue was taken up in ethyl acetate, washed twice with 100 ml portions of saturated aqueous NH4Cl solution, twice with 100 ml portions of saturated aqueous NaHCO3 solution and once with 100 ml of brine. The organic phase was dried (NaSO4), filtered, and concentrated to afford an oil which was purified using preparative HPLC (silica gel, 3% methanol in dichloromethane as the loading solvent and eluent). The appropriate fractions were combined and the solvents removed under reduced pressure yielding 2.93 g of 1,2,3,3a,8,8a-hexahydro-α-oxo-1,3a,8 -trimethyl-5-pyrrolo[2,3-b]indole acetic acid, n-hexyl ester, as an oil.

Provenance & Evidence