Compound 8b
anti-(±)-tetrahydrofuran-2,5-diyl diacetate
From: Simplified immunosuppressive and neuroprotective agents based on gracilin A
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Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.
To a suspension of Pb(OAc)4 (2.00 g, 4.54 mmol, 1.10 equiv) in glacial AcOH (10.0 mL) was added furan 10 (0.30 mL, 4.13 mmol, 1.00 equiv) and the mixture was stirred at 23 ºC for 18 h. AcOH was evaporated and Et2O was added to the residue. The precipitate was filtered, the filtrate was collected, evaporated and the residue was redissolved in anhydrous EtOAc (50 mL). 5% Rhodium on alumina (180 mg) was added and the hydrogenation was carried out under hydrogen atmosphere (1 atm, balloon) for 24 h. The solution was filtered through Celite, the filtrate was concentrated by rotary evaporation and purified by an automated flash chromatography system (5→50% EtOAc/hexanes) providing 721 mg (94% yield, 2 steps) of (±)-8a and (±)-8b as a clear colorless oil and as a mixture of two isomers (ratio 1.7:1 cis:trans, according to 500 MHz 1H-NMR). IR (thin film): 2921, 2851, 1745 cm–1; HRMS (ESI+) m/z calcd for C8H12LiO5 [M+Li]+: 195.0847, found: 195.0845. Spectral data matched that previously reported (Lee, S., Kaib, P. S. J. and List, B. J. Am. Chem. Soc., 2017, 139, 2156-2159.).
