P. Renaut

Chlorures de mono- et dialkyl-zirconocene et-hafnocene

Condensation of cyclopentadienyl anions obtained from fulvenes and tetra- chloride metal to prepare (η5-RC5H4)2MCl2, R = alkyl; M = Zr or Hf is described. The prochiral complexes (η5-RC5H4) (η5-C5H5)MCl2 are prepared in a similar way from MCl4 (M = Zr), but the best method uses (η5-C5H5)ZrCl3 or (η5-C5H5)HfCl3, 2THF. Preparation of this adduct is described.

Structure cristalline et proprietes du dichlorure de bis(pentahapto-benzylcyclopentadienyl)zirconium triboluminescent

Abstract The product ( n 5 -C 5 H 4 CH 2 C 6 H 5 ) 2 ZrCl 2 is orthorhombic: a 12.05(1), b 24.12(2), c 6.99(1) A; space group Aba 2, Z 4. Final R 0.077. The Zr atom is tetrahedrally coordinated by two Zrue5f8Cl σ bonds and two Zrue5f8Cp π bonds. The crystal is tri-boluminescent and highly piezoelectric.

Composes chiraux du zirconium et du hafnium

Abstract The first chiral dicyclopentadienyl compounds of zirconium (IV) and hafnium(IV) of the form (η 5 -C 5 H 5 ) (η 5 -RC 5 H 4 )MClX (X = alkoxy, aryloxy or benzyl group) have been prepared and studied. The presence of an asymmetric metal atom is shown by NMR of these complexes containing suitable ligands.

Towards a new type-of HMG-COA reductase inhibitor

Abstract In an attempt to design a novel class of HMG-Co A reductase inhibitors, we have synthesized compound as a reaction intermediate analogue of the enzymatic reduction of mevaldic acid by NADPH. A 15 steps, enantioselective sequence allowed us, from commercial R-(+)-malic acid to prepare aldehyde in an optically pure form and to couple it with the nicotinamide moiety affording the target molecule.

Formation of a zirconium—molybdenum bond via methane elimination

Reaction of (n5-C5H5)2Zr(CH3)2 and (n5-C5H5)Mo(CO)3H gives (C5H5)2CH3Zr--Mo(C5H5)(CO)3. Some properties of this compound are described.

Cyclopentadienylhafnium trichloride, its synthesis and use to prepare a chiral hafnium compound

The preparation and characterisation of the new hafnium compound (η5-C5H5)HfCl3,2THF is reported; it has been used to prepare the first chiral complex of hafnium.

A new efficient synthesis of the immunosuppressive agent (±)-15-deoxyspergualin

Abstract (±)-15-Deoxyspergualin is a new promising immunosuppressive agent, recently marketed in Japan for the control of corticoresistant acute renal graft rejection. We describe here a nine-step synthesis starting from 7-bromoheptanenitrile and N1,N4-bis(benzyloxycarbonyl)spermidine, suitable for the production of multigram quantities of this unstable highly polar compound with an 18% overall yield. Furthermore, it opens the way for the synthesis of α-hydroxyglycine analogues.

Asymmetric total synthesis of natural diheteropeptin

Abstract A total asymmetric synthesis of diheteropeptin and a stereomer from the known ( E )-1-iodo-6-octene, using the Schollkopf method for amino acid synthesis and Sharpless asymmetric dihydroxylation as key steps, is described. The asymmetric synthesis of a new unsaturated amino acid is also described.