Trifluoroacetic acid → 3-[(Fluoren-9-ylmethyl)oxycarbonyl]pyrrolo[3,2-e]indoline-7-carboxylic acid

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Reaction Steps

3-(tert-Butyloxycarbonyl)pyrrolo[3,2-e]indoline-7-carboxylic acid 8 (Boger et. al, J. Org. Chem. 52:1521 (1987)) (0.76 g, 2.4 mmol) was deprotected by a treatment with 5 mL of TFA for 1 h. TFA vas evaporated and the resultant trifluoroacetate dissolved in a mixture of 11% Na2CO3 (10 mL) and 5 mL of THF. 9-Fluorenylmethyl chloroformate (0.75 g, 2.9 mmol) was added and the reaction mixture was stirred for 3 h. The reaction was diluted with water (200 mL) and extracted with ethyl ether (2×50 mL). The aqueous phase was acidified by adding 1N HCl to pH 1-2. Precipitated product was collected by centrifugation, washed with water and dried under vacuum to afford 0.86 g (83%) of 9 as a yellow-gray solid.

Provenance & Evidence