Stereoselective Synthesis of Functionalized trans-2, 5-Disubstituted Tetrahydrofurans

摘要

The addition of the titanium enolates of N-acetyl, N-propionyl, and N-bromoacetyl (R)-oxazolidin-2-ones to γ-lactol 2, derived from (S)-glutamic acid, afforded trans- and cis-2, 5-disubstituted tetrahydrofurans (trans/cis ratio: R = H, 2 : 1, R = Me, 8 : 1; R = Br, 10 : 1) after desilylation with aqueous HF/CH_3CN. Chromatographic separation and LiBH_4 reduction allowed the efficient preparation of the corresponding trans-2, 5-disubstituted tetrahydrofuran diols and the recovery of the chiral auxiliary.