Total Syntheses of (+)- and (-)-Tetrapetalones A and C.

Described herein are syntheses of the naturally occurring polyketides (-)-tetrapetalones A and C and their respective enantiomers. The employed strategy involves initial assembly of a masked N-aryl tetramic acid which is advanced via a highly selective conjugate addition/intramolecular Friedel-Crafts acylation sequence to deliver a key azepine intermediate. Application of recently developed C-H activation chemistry and subsequent Heck cyclization delivers the aglycone framework in an overall 12 steps. Resolution of the aglycone via stereospecific glycosylation with an enantiopure glycosyl donor followed by separation of the derived diastereomers enables further advancement to either (+)- or (-)-tetrapetalones A and C.

Total syntheses of (±)-securinine and (±)- allosecurinine.

Total syntheses of (±)-securinine and (±)-allosecurinine that employ a tandem rhodium carbenoid-initiated Claisen/α-ketol rearrangement sequence as a key step are described.

P-stereogenic trifluoromethyl derivatives of Josiphos: synthesis, coordination properties, and applications in asymmetric catalysis.

Intermolecular nucleophilic substitution of a CF(3) group of bis(trifluoromethyl)phosphanes by a lithiated Ugi's amine (4) affords both diastereoisomers of the corresponding P-stereogenic trifluoromethylphosphanes 6 and 7. Separation of the isomers by column chromatography on silica gel followed by substitution of the dimethylamino group with phosphanes or pyrazoles yields the bidentate P^P (9 and 10) or P^N ligands (12 and 13) without epimerization at the stereogenic phosphorus center. The coordination properties of these bidentate ligands were investigated on the basis of crystal structures of the corresponding palladium and rhodium complexes. IR spectroscopic measurements of rhodium-carbonyl complexes 16-23 indicated the strongly electronic-withdrawing character of these phosphanes. The catalytic potential of these ligands was demonstrated in the rhodium-catalyzed hydrogenation of olefins as well as in the palladium-catalyzed allylic alkylation reaction, where high activities and enantioselectivities were observed.

Chiral trifluoromethylphosphines: a new stereoselective synthesis of Josiphos-type ligands containing two stereogenic phosphorus atoms.

Intramolecular nucleophilic substitution of a trifluoromethyl group to form a 1,2-diphosphole derivative followed by the sequential addition of an alkylating agent and a carbanion are the key steps in the stereoselective synthesis of novel ferrocenyl diphosphines for asymmetric catalysis.