2009

ABSTRACT:

We have developed the first enantioselective Brønsted acid-catalyzed electrocyclization-protonation reaction which provides a number of differ-ent cyclopentenones in good yield and with highenantioselectivities (67–78% ee). Special features ofour newly developed organocatalytic Brønsted acid-catalyzed protonation are the low catalyst loadings as well as the mild reaction conditions.

ABSTRACT:

We report on the development of a new metal-free, highly enantioselective, Brønsted acid catalyzed condensation/amine addition reaction for the synthesis of 2,3-dihydroquinazolinones starting from the simplest and most readily available starting materials. Thus, a highly efficient and general approach to valuable enantiomerically enriched 2,3-dihydroquinazolinones with preference for the more active S enantiomers has been established. This extremely simple and practical protocol is not only of great importance and considerable interest for additional drug design and development of dihydroquinazolinones, but it also simplifies further examination of tubulin polymerization inhibition in antitumor research. This in turn may provide insights into the mechanism of the ligand binding at the colchicine binding site. Moreover, certain dihydroquinazolinones show an inherent fluorescence which allows explicit intracellular localization.

ABSTRACT:

We report a new diastereo- and enantioselective Lewis base catalyzed domino Michael/aldol reaction in which the formation of four stereogenic centers is controlled. Several α,β-unsaturated aldehydes can be used to provide access to chiral bicyclo[3.2.1]octane-6-carbaldehydes in good yields and with excellent enantioselectivities (90–98 % ee). In addition, we described the targeted synthesis of bicyclic diols and triols, as well as introduced a new retro-aldol/cyclization reaction which enables easy access to valuable tetrahydrochromenones. Finally, our newly developed organocatalytic domino reaction allows the synthesis of chiral polysubstituted seven-membered rings that are generally difficult to synthetically access and which can be used in the future synthesis of natural products.

ABSTRACT:

We describe a highly efficient, enantioselective hydrogenation for the synthesis of terminal 1,2-diols. Applying new, nonsymmetric diphosphine ligands, which are based on a chiral phospholane unit and a variable second donor function and which can be readily produced on a large scale, we were able to develop an asymmetric hydrogenation in which not only diverse aromatic but also aliphatic α-hydroxy ketones can be transformed into valuable 1,2-diols with excellent enantioselectivity.17 Furthermore, the catalyst loading could be reduced to 0.01 mol % without loss of enantioselectivity. This underscores the preparative application of this methodology.