Highly diastereoselective synthesis of chiral furans with a quaternary carbon substituent at the 2-position using 8-phenylmenthol as the chiral auxiliary
The reaction of cis-4-oxo-2-pentenal and 8-phenylmenthyl 2-oxocyclopentane-1-carboxylate in the presence of a fluorinated cosolvent afforded the corresponding furan product with a high diastereoselectivity of up to 96% de. Other cyclic β-ketoesters reacted in a likewise diastereoselective manner.