Diastereoselective formation of contiguous quaternary centers: the modified carroll rearrangement

Regioselective base-free intermolecular aminohydroxylations of hindered and functionalized alkenes

Regioselective base-free intermolecular aminohydroxylations of functionalized trisubstituted and 1,1-disubstituted alkenes employing benzoyloxycarbamate 3a and catalytic OsO(4) are described. In all cases, the more substituted alcohol isomer is favored. Sluggish reactions could be promoted by gentle heating, the use of amine ligands, or increased catalyst loadings. A competitive rearrangement was observed with a secondary allylic alcohol substrate. The adducts serve as useful precursors to dehydroamino acids.

Total Synthesis of Zincophorin and Its Methyl Ester

A total synthesis of the naturally occurring ionophore zincophorin has been realized. The route features an intramolecular oxymercuration of a cyclopropanemethanol and a Carroll-Claisen rearrangement for the respective elaboration of the C1-C12 and C13-C25 subunits, which have been assembled by using a highly diastereoselective titanium-mediated aldol condensation.

α-Heterosubstituted Aldehydes in Organic Synthesis. Enantioselective Approaches to New Analogues of Mevinic Acids

Various aldol approaches towards the asymmetric synthesis of the lactone moiety of HMG-CoA-reductase inhibitors are described. Auxiliary controlled as well as catalytic aldol reactions resulted only in modest to low selectivities, whereas 1,2-additions to readily available highly enantiomerically enriched α-heterosubstituted aldehydes yielded δ-hydroxy-β-ketoesters with a high degree of diastereocontrol and in good chemical yields. The novel mevinic acid analogues could then be obtained bysyn-reduction of the addition products.