A. Tomas

A simple and efficient asymmetric synthesis of 3-alkyl-isoindolin-1-ones

A simple asymmetric access to 3-alkyl-isoindolin-1-ones was investigated through the diastereoselective alkylation of 2-[(1R)-2-hydroxy-1-phenylethyl]-2,3-dihydro-1H-isoindolin-1-one 5. High diastereoselectivities were observed with LDA or LiHMDS while the isolated yields were modest (about 50%). In contrast the use of NaHMDS gave good isolated yields (up to 85%) but lowered diastereoselectivities. This methodology offers an efficient asymmetric synthesis of 3-alkylated isoindolin-1-ones.

N-[2-(Indan-1-yl)-3-mercapto-propionyl] amino acids as highly potent inhibitors of the three vasopeptidases (NEP, ACE, ECE): In vitro and In vivo activities.

We have previously reported the design of a lead compound 1a for the joint inhibition of neprilysin (NEP, EC 3.4.24.11), angiotensin converting enzyme (ACE, EC 3.4.15.1) and endothelin converting enzyme (ECE-1, EC 3.4.24.71), three metallopeptidases which are implicated in the regulation of fluid homeostasis and vascular tone. We report here the synthesis and biological activities of analogues derived from this lead with inhibitory potencies in the nanomolar range for the three enzymes. Compounds 8b and 15c are the most potent triple inhibitors described to date.

Determination des structures des formes α et β de Ga2S3 structural determination of α and β Ga2S3

Resume The structures of αGa 2 S 3 and βGa 2 S 3 were refined in order to establish the exact cationic distribution. The R factors are 0.046 for αGa 2 S 3 and 0.049 for βGa 2 S 3 . βGa 2 S 3 is of wurtzite type and αGa 2 S 3 is found to be a superstructure of βGa 2 S 3 with a partial occupation of the three cationic sites.

Les Composés de la Metformine avec les Ions CoII, CuII et NiII

The structures of trichloro(N,N-dimethylbiguanidium)-cobalt(II), [Co(C 4 H 12 N 5 )Cl 3 ], (I), and di-μ-chlorobis-[chloro-(N,N-dimethylbiguanide)copper(II)], [CuCl 2 -(C 4 H 11 N 5 )] 2 , (II), consist of the metal atom bound to three Cl atoms and to one or two N atoms, respectively, belonging to one metformine ligand. The structures of bis(N,N-dimethylbiguanide)copper(II) dichloride dihydrate [Cu(C 4 H 11 N 5 ) 2 ]Cl 2 .2H 2 O, (III), and bis-(N,N-dimethylbiguanide)nickel(II) monohydroxide chloride, [Ni(C 4 H 11 N 5 ) 2 ](Cl)(OH), (IV), are formed of [M(metformine) 2 ] 2+ (M = Cu or Ni) and anions (Cl- or OH - ). In these compounds, the metal is on a centre of symmetry and forms a square-planar structure comprising four N atoms of two N,N-dimethylbiguanidine ligands. The metformine ligand is planar in (II), (III) and (IV), allowing delocalization of the π-electron system in the metal-ligand ring, but not in (I), where the dihedral angle between the two guanidine groups is 68.4(2)°. The four structures are stabilized by hydrogen bonding and van der Waals interactions.

L'hydrogénocarbonate de Bis(N,N-diméthylbiguanide) Cuivre(II), [Cu(C4H11N5)2]2HCO3

The structure of bis(N 1 ,N 1 -dimethylbiguanide- N 2 ,N 4 )copper(II) bis(hydrogencarbonate) consists of a [Cu(C 4 H 11 N 5 ) 2 ] 2+ cation and two HCO 3 + anions. The Cu atom is at a centre of symmetry and forms a square-planar structure with four N atoms belonging to two N,N-dimethylbiguanide (metformin) groups. The metformin ligand is planar, allowing delocalization of the π electrons in the metal-ligand ring. The hydrogencarbonate anions are hydrogen bonded to N(I), N(2) and N(3)

Structure du compose Yb0,875S structure of Yb0,875S

Abstract The structure of Yb0.875S has been refined in order to establish the exact cationic distribution. The R factor is 0.042 for 78 reflections. The structure is found to be a superstructure of NaCl type and the cubic cell edge is 11.250(3) A. Alternative cationic planes {111} having respectively a high and a low number of vacancies explain the superstructure. No distortions or vacancies are observed for the S lattice.

Polymorphisme de Ga2S3 et diagramme de phase GaS polymorphism of Ga2S3 and phase diagram of GaS

Abstract The monoclinic form α′ Ga2S3 is exactly stoechiometric and is stable from room temperature to melting. The hexagonal form α and the wurtzite-type form β exist only at high temperature, above 885°C; their formation requires a very small defect of sulphur and consequently their are obtained in presence of GaS. The passage from the hexagonal form to the wurtzite form is progressive and depends on the proportion of GaS. The blende-type form is clearly sub-stoechiometric (GaS1.38) and only exits in a small domain of temperature. The phase-diagram is described from GaS0.96 to GaS1.56.

Cristallochimie des sulfures mixtes de chrome et d'erbium

Abstract Inventory of a family of mixed chromium-erbiumsulfides (belonging to orthorhombic or monoclinic systems). Two of three parameters keep constant values, only the third (b) changes. The erbium atoms occupy octahedral regular and prismatic seven-coordinated sites. Chromium atoms are at the center of octahedral sites sometimes deformed by Jahn-Teller effect. We show how these structures are built from same basal pattern. An agreement between geometric pattern and chemical formula is laid down, it allows to confirm value of b parameter.

Structural studies by X-ray diffraction and Mössbauer spectroscopy of cubic FeYb2S4 and FeLu2S4

Abstract The two isostructural compounds FeYb2S4 and FeLu2S4 were studied by X-ray diffraction and Mossbauer spectroscopy. The structure was solved in the space group Fd3m; Z = 8. For the FeYb2S4, the S atoms occupy the (32e) positions. The tetrahedral (8a) and octahedral (16d) positions of the direct spinel are, respectively, occupied by 0.8 Fe2+ and (0.88 Yb3+ + 0.045 Fe2+). The additional octahedral (16c) positions are occupied by (0.12 Yb3+ + 0.55 Fe2+). For 155 reflections crystallographic R is 0.034. The Mossbauer spectrum results from the superposition of four doublets. Two doublets with the same isomer shift of 0.73 mm/sec are characteristic of Fe2+ ions in the (8a) position with two distorted tetrahedral symmetries simulated by two different quadrupole splittings. The third and fourth doublets correspond to Fe2+ ion in 16c and 16d positions. The intensity ratio between the doublets is in agreement with the distribution (Fe0.82+ □0.2) (Yb1.763+Fe0.092+□0.15) (Yb0.243+Fe0.112+□1.65) which corresponds to FeYb2S4. The metal atoms in FeLu2S4 are distributed in the same way as those in FeYb2S4.

Structure cristalline du spinelle CdEr2S4

Abstract The crystal structure of CdEr 2 S 4 is solved from single crystal determinations. The R factor is 0.06 for 120 independent reflections. It is normal spinel, with regular occupancy of the sites. Interatomic distances are : 2.67 A for ErS, and 2.57 A for CdS.