DIISOPROPYL TARTRATE MODIFIED (E)-GAMMA-[(CYCLOHEXYLOXY)DIMETHYLSILYL]ALLYLBORONATES AND (E)-GAMMA-(DIMETHYLPHENYLSILYL)ALLYLBORONATES - CHIRAL REAGENTS FOR THE ENANTIOSELECTIVE AND DIASTEREOSELECTIVE SYNTHESIS OF ANTI 1,2-DIOLS AND 2-BUTENE-1,4-DIOLS VIA THE FORMAL ALPHA-HYDROXYALLYLATION AND GAMMA-HYDROXYALLYLATION OF ALDEHYDES

Enantioselective syntheses of 4-substituted (E)-2-butene-1,4-diols and anti 1,2-diols are described. Highly diastereoselective reactions of aldehydes and the chiral PhMe2Si- and (C6H11O)Me2Si-substituted allylboronates 25 and 26 provide anti homoallylic silanols 29 and 50, respectively. Epoxidation of 29 with dimethyl dioxirane followed by acid catalyzed Petersen rearrangement of the intermediate epoxysilanols provides butene-1,4-diols 27 with excellent enantioselectivity (81-87% e.e.). Tamao oxidation of 50 provides anti diols 22 (64-72% e.e.). These procedures give excellent results especially in matched double asymmetric reactions with a range of oxygenated, chiral aldehydes (Figures 1 and 2). These methods promise to find application in diastereoselective syntheses of carbohydrates from acyclic precursors.