Chirality at phosphorus: hybrid duplexes of chimeric oligonucleotides containing methylphosphonothioate linkages with complementary DNA and RNA

Chimeric oligonucleotides with incorporated diastereomerically pure dinucleoside(3′,5′)-methylphosphonothioates and their oxo- and seleno- congeners of known absolute configuration are reported. The relation between stability of the hybrid duplexes with complementary DNA and RNA and their structure is analyzed in context of absolute configuration of the P-chiral internucleotide bonds.     

Novel method for the synthesis of dinucleoside-(N3′ → P5′)-phosphoramidothioates

A new approach for the synthesis of dinucleoside-(N3′ → P5′)-phosphoramidothioates based on the Atherton–Todd reaction has been developed using nucleoside H-thiophosphonates and 3′-amino-2′,3′-dideoxynucleosides with an unprotected 5′-hydroxyl group. A mixture of P-diastereomers of dinucleosides was separated by column chromatography into fast migrating and slow migrating isomers. Based on single crystal X-ray diffraction analysis, the absolute configuration at the phosphorus atom in the slow eluting diastereomer of the dinucleoside-(N3′ → P5′)-phosphoramidothioate G_NPSG_NHTr was assigned as Rp.     

Thermal rearrangement of bis(hydroxymethyl)phosphines as a way to P-chiral phosphine oxides

Bis(hydroxymethyl)(2-pyridyl)- and bis(hydroxymethyl)-[(2-pyridyl)ethyl]phosphines on heating to 180 °C undergorearrangement leading to racemic P-chiral tertiary P-methyl-P-(hydroxymethyl)-containing phosphine oxides. The spontaneous self-resolution of these enantiomer mixtures during the crystallization was demonstrated.     

Cooperative Effects between Chiral Cpx–Iridium(III) Catalysts and Chiral Carboxylic Acids in Enantioselective C−H Amidations of Phosphine Oxides

An enantioselective C−H amidation of phosphine oxides by using an iridium(III) catalyst bearing an atropchiral cyclopentadienyl (Cp^x) ligand is reported. A very strong cooperative effect between the chiral Cp^x ligand and a phthaloyl tert-leucine enabled the transformation. Matched–mismatched cases of the different acid enantiomers are shown. The amidated P-chiral arylphosphine oxides are formed in yields of up to 95 % and with excellent enantioselectivities of up to 99:1 er. Enantiospecific reduction provides access to valuable P-chiral phosphorus(III) compounds.     

Access to P‐ and Axially Chiral Biaryl Phosphine Oxides by Enantioselective CpxIrIII‐Catalyzed C−H Arylations

An enantioselective C?H arylation of phosphine oxides with o‐quinone diazides catalyzed by an iridium(III) complex bearing an atropchiral cyclopentadienyl (Cp^x) ligand and phthaloyl tert‐leucine as co‐catalyst is reported. The method allows access to a) P‐chiral biaryl phosphine oxides, b) atropo‐enantioselective construction of sterically demanding biaryl backbones, and also c) selective assembly of axial and P‐chiral compounds in excellent yields and diastereo‐ and enantioselectivities. Enantiospecific reductions provide monodentate chiral phosphorus(III) compounds having structures and biaryl backbones with proven importance as ligands in asymmetric catalysis.