Organophosphorus compounds based on 1,4- and 1,5-diketones

The phosphorylation reactions of 1,4- and 1,5-diketones with dimethyl phosphites, hypophosphorous acid and its esters, and phosphines are discussed. The reactions lead usually to the formation of cyclic compounds. Dedicated to the memory of Academician M. I. Kabachnik on his 90th birthday. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1905–1910, October, 1998.     

Stitching phospholanes together piece by piece: new modular di- and tridentate stereodirecting ligands

The modular one-pot synthesis of a large family of bi- and tridentate 2,5-dimethyl- and 2,5-diphenyl-substituted phospholanes employs air-stable chiral phospholanium chloride salts and primary amines or NH(4)Cl as starting materials. These were transformed into the C(2)-symmetric dimethyl- and diphenylphospholane ligands, which reacted with [Rh(cod)(2)]BF(4) (cod=1,5-cyclooctadiene) to yield the rhodium complexes [Rh(L)(cod)]BF(4) (L=bisphospholane ligands). The corresponding trisphospholane complexes, 11 and 12, were obtained in high yields (81 and 92%, respectively), and fully characterised by NMR spectroscopy, mass spectrometry and elemental analysis. Whilst in the C(3)-symmetric complex 11, containing the tridentate 2,5-dimethylphospholane, the ligand is bound symmetrically, different coordination behaviour was found for the diphenyl-substituted complex 12, in which the coordination of only two of the three phospholane moieties to the metal centre was observed. A DFT study at the B3PW91 level established minimum energy structures consistent with experimental findings in solution and in the solid state. The non-coordinated phospholane unit present in 12 allowed further modification of the complex through the coordination of Au(I)-X (X=Cl, C(6)F(5) and tris(trifluoromethyl)phenyl ((F)Mes)) fragments to the pendant phosphane. To investigate the potential of the new ligands, the enantioselective hydrogenation of a series of prochiral olefins as benchmark substrates, using isolated Rh complexes as catalysts, was studied. The substrates included methyl esters of three dehydro-α-acetamido acids and two itaconic acid derivatives. In general good to excellent enantioselectivities (of up to >99% ee) were observed. Ligand backbone modification by coordination of bulky Au-X substituents to the free phospholane unit in complex 12 led to an outstanding enhancement of the catalyst performance and there was a clear correlation between the properties of the complex periphery and the enantioselectivity.     

Ribozymomimetic Chemical Synthesis of Peptide Bond Using Phosphorous Acid/Oxirane Mediators

Abstract

A model system is created that mimics natural ribosome as well as the way of ribozyme action. It uses oxirane analogue as condensation reagent and H₃PO₃ as activator for the carboxyl group and as protecting reagent for the NH₂ function. In order to demonstrate the ability of the H₃PO₃/oxirane system to mimic natural peptide bond synthesis on the ribosome as well as to mimic the ribozyme synthesis and hydrolysis of an inter biomonomeric bond, four model compounds containing an amide bond were synthesized using phosphorous acid/oxirane mediators.

GRAPHICAL ABSTRACT