Synthèse du mèthyl-1 diformyl-2,3 pyrrole,de la méthyl-1 pyrrolo[2,3-d] pyridazine et de la méthyl-1 oxo-6 (6h)cycloheptatrieno[b] pyrrole

This communication describes the synthesis of l-methyl-2,3-diformylpyrrole. This new compound is used to prepare a new heterocycle, l-methylcyclohepta[b]pyrrol-6-one and thus allows a new synthesis of l-methylpyrrolo[2,3-d]pyridazine.     

1H-NMR,Ultraviolet and infrared spectra of some (Z)-α-(phenyl)-β-(2-furyl), -(2-pyrrolyl) and -(N-methyl-2-pyrrolyl)acrylonitriles

The ¹H-nmr data of some (Z)-α-(p-substituted-phenyl)-β-(2-furyl), -(2-pyrrolyl), and -(N-methyl-2-pyrrolyl)-acrylonitriles have been investigated to indicate the preferred conformation and to establish the conformational preferences of the β-heterocyclic ring. The ultraviolet spectra have been discussed in order to obtain information about the chromophores responsible for the absorption. The infrared spectra have been analyzed for the identification of the main absorption frequencies of cyano and ethylenic groups and to assign the characteristic absorption bands to specific normal vibrations of the heteroaromatic nuclei.     

Structure of Lipid A from Pseudomonas corrugata by electrospray ionization quadrupole time-of-flight tandem mass spectrometry

The use of the electrospray ionization quadrupole time-of-flight tandem mass spectrometry (ESI-QTOFMS) technique for the structural determination of Lipid A from Pseudomonas corrugata is described. This technique appears to be more sensitive with respect to other commonly used tandem mass spectrometric approaches, and was very valuable in the structural determination of the highly heterogeneous Lipid A fractions. The Lipid A fraction consists mainly of a pentaacyl component in which 3-hydroxydecanoyl [10:0(3-OH)] and 3-hydroxydodecanoyl [12:0(3-OH)] are linked as primary acyl substituents to the classical bisphosphorylated beta-(1' --> 6)-linked D-glucosamine disaccharide. Secondary substitution of N-acyl fatty acids with dodecanoyl residues [12:0] and/or its 2-OH derivatives was also observed.     

Selectivity in cycloadditions-IX: Cycloadditions of nitrile oxides to indoles. Reactivity and regiochemistry

Cycloadditions of benzonitrile oxide and mesitonitrile oxide to N-methylindole and indole yield the acid sensitive cycloadducts 1 a-d with high regioselectivity. With N-carbethoxyindole the stable cycloadducts 1 e,f and minor amounts of the regioisomeric 2 e,f are isolated. The electron withdrawing substituent reduces both the regioselectivity and the reactivity of the cycloadditions.Frontier orbital considerations, based on MINDO/3 calculations, allow elucidation of the observed changes in reactivity and regiochemistry.     

13C NMR examination of some N-thioaroylmorpholine–bromine adducts

The ¹³C NMR chemical shifts of three N-thioaroylmorpholine–bromine adducts, previously used as synthetic intermediates, are compared and discussed in the light of the corresponding shifts of the parent thioamides and suitable model compounds. Chemical shift changes are interpreted in terms of the electronic perturbation resulting from bromine coordination at sulphur.