Alain Neuman

Microbial transformation of diterpenes: Hydroxylation of sclareol, manool and derivatives by Mucor plumbeus

Abstract Microbial transformation of several labd-14-ene derivatives has been carried out with a Mucor plumbeus strain, Sclareol (1) (labd-14-en-8α,13β-diol) affords quantitatively a mixture of triols from which the labd-14-en-3β,8α,13β-triol (2) is obtained in high yield. Incubation of other labdane derivatives, including manool (6) [labd-8(17),14-dien-13β-ol], the corresponding 7α-hydroxy derivative (10), manoyl oxide (14) or sclareolide (15) with the same microorganism results in a mixture of various new hydroxylated and keto- derivatives.

Tracheobronchial FDG uptake in primary amyloidosis detected by PET/CT.

Tracheobronchial amyloidosis is a rare manifestation of the disease and has never been described with FDG PET/CT. In this study, we report a case of a 70-year-old man with increasing dyspnea, a right pleural effusion, a tracheobronchial circumferential wall thickening, and a mediastinal fat infiltration on CT scan. FDG PET/CT revealed intense tracheobronchial uptake associated with mediastinal and intra-abdominal fat uptake. Bronchoscopy and mediastinoscopy with biopsies confirmed the diagnosis of primary amyloidosis and excluded malignancy. FDG PET/CT could be useful for the evaluation of tracheobronchial amyloidosis metabolic activity and follow-up.

Structure cristalline de la 2-acétamido-1-N-(l-aspart-4-oyl)-2-désoxy-β-d-glucopyranosylamine

Abstract The crystal data of 2-acetamido-i- N -( l -aspart-4-oyl)-2-deoxy-β- d -glucopyranosylamine are a 4.932 (2), b 24.218 (8), c 7.788 (3) A, and β 97.718° (5), space group P2 1 , Z 2. The structure was solved by direct methods and refined to an R value of 0.06 for 1679 independent reflexions. The pyranose form adopts the 4 C 1 ( d ) conformation and the asparagine residue has an extended conformation. The N -glycosyl bond was compared with the corresponding bond of the acetamido group and the β- d -(1→x)-glycoside linkages in oligosaccharides. The acetamido group, the asparagine residue, and some hydrogen intermolecular-bonds determine channels parallel to the crystallographic axis, a , which accept water molecules partially disordered, as in some inclusion compounds.

Structure cristalline d'une deuxième forme de mélézitose monohydrate. Effet de l'environnement sur la géométrie d'un oligosaccharide

Abstract Melezitose [O-α- d -glucopyranosyl-(1→3)-β- d -fructofuranosyl α- d -glucopyranoside] monohydrate crystallizes in two polymorphic forms (I and II). The structure of form II, studied by X-ray crystallography, shows an orthorhombic cell having a 7.135 (4), b 15.362 (8), c 19.134 (8) A, space group P212121, and Z 4. The structure, solved by direct methods, was refined to a final value of R 0.045. The molecule of form II seems to be more constrained by its crystalline environment than that of form I. These constraints imply not only little variations in glycosidic bonds, but also a change of conformation for the furanose ring, and a perceptible deformation of the sucrose pyranose ring. This study gives an example of estimation of oligosaccharide molecular-flexibility.

Diastereoselective synthesis of a taxane precursor

Abstract A highly diastereoselective synthesis of the taxane potential precursor 16 is achieved. An unexpected diastereoselectivity was observed upon condensation of the α-trimethylsilyloxyaldehydes 9a or 9b with the cyclohexenyllithium 10 . The single diol isomers 13A and 14A exhibiting the required 1β,2α relative configuration are obtained in good yields.

Structure cristalline du méthyl-3-O-α-d-glucopyranosyl-α-d-glucopyranoside (méthyl-α-nigéroside)

Abstract The crystal structure of methyl 3- O -α- d -glucopyranosyl-α- d -glucopyranoside (methyl α-nigeroside) was studied by X-ray crystallography. The crystal data are a 6.591 (2), b 13.243 (4), and c 9.446 (2) A, β 108.0° (1), space group P2 1 , Z 2. The structure, solved by direct methods, was refined to an R final value of 0.04. A hydrogen bond links the two d -glucopyranose rings of the same molecule. The orientation at C-1′ue5f8O-3ue5f8C-3 has been compared with that of disaccharides having an α- d -(1→x)-linkage. The valence angle C-1′ue5f8Oue5f8C-x varies to some extent in relation with the steric interaction of the bridge O-3. The glycosidic torsion angles are both influenced by the exoanomeric effect and the existence of an intramolecular hydrogen bond between the two rings. The latter disturbs the exoanomeric effect and modifies the torsion and pseudotorsion angles.

Dual-isotope myocardial imaging: feasibility, advantages and limitations

Two hundred and thirty-one patients underwent dual-isotope myocardial imaging (rest thallium-201 followed by stress technetium-99m sestamibi). The feasibility of the procedure was excellent: camera scheduling flexibility was improved and the duration of the procedure was less than that of a classical stress-redistribution procedure. Interpretation of defects due to image attenuation was facilitated by the different attenuation properties of 201Tl and 99mTc-sestamibi in 11 of 19 patients. 210Tl cross-over on 99mTc was found to be 15% ± 3% with doses of 201Tl and 99mTc-sestamibi of 3 and 10 mCi, respectively, and 7% ± 2% with doses of 3 and 20 mCi. This protocol should preferentially be reserved for patients with a history of myocardial infarction and/or a basal left ventricular dysfunction, in whom assessment of myocardial viability is of major interest. Extensive clinical validation of the dual-isotope procedure is required and optimal acquisition and reconstruction parameters should be established.

Diagnosis of synchronous isolated splenic metastasis from lung adenocarcinoma: complementary role of FDG PET/CT and diffusion-weighted MRI.

Isolated splenic metastasis is extremely rare. In this study, we report a case of a 52-year-old man referred for Pancoast Tobias Syndrome by which FDG PET/CT detected an isolated splenic metastasis. Diffusion-weighted MRI confirmed the isolated splenic lesion. A low apparent diffusion coefficient was consistent with a tumor lesion. CT-guided biopsy of both the lesions and histopathologic findings confirmed a lung adenocarcinoma with an isolated splenic metastasis. This case reveals a very rare occurrence of isolated splenic metastases in the context of lung cancer and illustrates the role of multimodality functional imaging for the early detection of uncommon metastasis.

1,3-Dipolar Cycloadditions VI (1). Structure and Conformation of Cycloadducts from Reactions of C-Aryl-N-phenylnitrones with Substituted Cinnamic Acid Amides

Summary.u2002Studies on cycloadditions of C,N-diarylnitrones to cinnamic acid amides were carried out. The diastereoisomeric (I, II) and (in some cases) regioisomeric (III) cycloadducts obtained were characterized by spectroscopic and X-ray data. Conformational studies were carried out by molecular modelling.

Conformational features of C-glycosyl compounds : crystal structure and molecular modelling of methyl C-gentiobiosidë

The crystal of methyl C-gentiobioside (methyl 8,12-anhydro-6,7-dideoxy-D-glycero-D-gulo-alpha-D-gluco-trideca pyranoside) (C14H26O10) is triclinic, space group P1, with a = 1.0181 (6) nm, b = 0.8093 (5) nm, c = 0.5066 (4) nm, alpha = 96.03 (5) degrees, beta = 99.94 (5) degrees, gamma = 90.85 (5) degrees. The two D-glucose residues have the 4C1 conformation. The orientation of the beta-(1----6) linkage is characterized by torsion angles phi = 55.9 degrees, psi = 175.1 degrees, and omega = -63.9 degrees. The orientation of the primary hydroxyl group at the non-reducing residue is gauche-trans (omega = -53.6 degrees). There is no intramolecular hydrogen bond. Molecules are held together by a network of hydrogen bonds involving all of the hydroxyl groups. This crystal structure is the first experimental characterization of a C-disaccharide. Unlike methyl gentiobioside, which has a high level of conformational flexibility, the C-disaccharide has a restricted flexibility. Each of the low-energy conformers in vacuo has a value of phi centered about 60 degrees, in agreement with the solid state conformation, and the exo-anomeric effect is no longer predominant.