(S)-2-Hydroxy-2-(6-(hydroxymethyl)-5-oxo-2,3-dihydro-5H-spiro[indolizine-1,2'-[1,3]dioxolan]-7-yl)-N-((S)-1-phenylethyl)butanamide → (4S)-4-Ethyl-7,8-dihydro-4-hydroxy-1H-pyrano(3,4-f)indolizine-3,6,10(4H)-trione

Participants

Reaction Steps

Three hundred milligrams of the compound (VII) obtained in the above procedure (1) were dissolved in 80% trifluoroacetic acid solution and the resulting mixture was stirred at room temperature for 2 hours under a nitrogen gas stream. The reaction mixture was concentrated to dryness and the residue was purified by column chromatography on silica gel (10 g). A colorless oily substance was obtained from a 98:2 eluate of chloroform and methanol. The oily substance was crystallized from a mixed solvent of ethanol and petroleum ether to obtain 170 mg of the title compound as colorless needle-like crystals.

Provenance & Evidence