Nouveaux dérivés de N‐phtalimido‐2‐arylepropanoate de pantolactonyle

We present the crystal and molecular structures of two new N‐phthalyl‐3‐amino‐2‐arylpropionic acid pantolactonyl ester derivatives with 4‐fluorophenyl and 3,4‐dimethoxyphenyl as the aryl group, 2,3,4,5‐tetrahydro‐4,4‐dimethyl‐2‐oxofuran‐3‐yl 3‐phthalimido‐2‐(4‐fluorophenyl)propanoate, C₂₃H₂₀FNO₆, and 2,3,4,5‐tetrahydro‐4,4‐dimethyl‐2‐oxofuran‐3‐yl 3‐phthalimido‐2‐(3,4‐dimethoxyphenyl)propanoate ethyl acetate hemisolvate, C₂₅H₂₅NO₈·0.5C₄H₈O₂. This structural study confirms the S configuration of the C2 and validates the stereospecificity of our synthesis strategy.     

7‐Methoxy­anthra­[1,9‐de]‐1,3,2‐dioxathiine‐8,11‐dione 2,2‐dioxide

The title compound, C₁₅H₈O₇S, contains the first structurally characterized example of a cyclic sulfate grouping fused to an aromatic ring system.     

Chromate de 2,2‐diméthylpropylènediammonium

The crystal structure of the title compound, 2,2‐dimethyl‐1,3‐propanediammonium chromate, (C₅H₁₆N₂)[CrO₄], consists of layers built up from CrO₄^2? tetrahedra alternating with diprotonated 2,2‐dimethylpropylendiamine molecules. N—H?O hydrogen bonds ensure the cohesion and stability of the structure.     

Etude par RMN. de polyaminocarboxylates de terres rares,III. Hydroxyéthyliminodiacétates de praséodyme

¹H—NMR. has been used to study the chemistry of the hydroxyethyliminodiacetate complexes of praseodymium in aqueous solution. The ligand exchanges by spontaneous dissociation of the metal-bis-hydroxyethyliminodiacetate (1:2 complex) and of the metal-bis-hydroxyethyliminodiacetate hydroxocomplex, by acid catalysed dissociation of the 1:2 complex, and by a bimolecular process involving the free ligand and the 1:2 complex or the ternary hydroxo-complex. The ligand exchange rate constants are given and the mechanisms discussed.     

Isolation and spectral study of 4‐methyl‐6,8‐dihydroxy‐7H‐benz[de]anthracen‐7‐one

4‐Methyl‐6,8‐dihydroxy‐7H‐benz[de]anthracen‐7‐one was isolated from the sap of Aloe by column chromatography. Its ¹H and ¹³C NMR spectra were completely assigned by utilizing two‐dimensional ¹H‐detected heteronuclear one‐bond (HMQC) and multiple‐bond (HMBC) chemical shift correlation experiments together with ¹H–¹H COSY and DEPT techniques. These techniques were also valuable in assigning the protons and carbons of those benzanthrone compounds which were previously incompletely reported because of the overlap of proton signals. The molecular structure was elucidated by 2D NMR analysis. The spectral properties (MS, IR and UV) are also presented. Copyright © 2003 John Wiley & Sons, Ltd.     

Détermination de la configuration de glycosylaziridines par dichroïsme circulaire. Note de laboratoire

CD.-Based Configurational Assignments of Glycosylaziridines The relationship between CD.-curves and the configuration of the trans-2-benzoyl-3-phenylaziridines was known. By studying a series of cis- and trans-2-glycosyl-3-benzoylaziridines we have shown that CD. allows the assignment of the configuration at both asymetric C-atoms. As benzoylaziridines can easily be obtained from cyano- or alkoxycarbonylaziridines without configurational change, the absolute configuration of these last two classes of compounds can also be assessed by this method.     

Isomérisation de 2,3‐époxypinanes fonctionnels en présence d'acides de Lewis

Isomerization of Functionalized 2,3‐Epoxypinanes in the Presence of Lewis Acids The functionalized 2,3‐epoxypinanes 1b – i were submitted to isomerization in the presence of ZnBr₂ at 110° (Table 1) or of BF₃⋅Et₂O at different temperatures (Table 2), and their behavior was compared with that of the non‐functionalized parent 1a and with similar known transpositions. The produced campholenals 2 , pinocamphones 3 , and in some cases, fencholenals 4 were isolated and characterized. A mechanism involving a concerted oxirane ring opening is proposed (Scheme 4).     

Synthèse spécifique de pyrimidines. Formation conccurentielle de pyrimidines et de triazépines

Nucleophilic displacement of ethyl cyanoacetic ester on compounds 1 or 2 with hydrazines yielded only pyrimidines 3, 4 or 11 . Triethyl orthoformate (or triethyl orthoacetate) reacting with o-aminohydrazides produced a mixture of pyrimidines 3 or 11 and the triazepine 10 .     

Epoxyesters p‐menthaniques et pinaniques en milieu basique – Parfum de noix de coco

Base‐Induced Reactions of p ‐ Menthane‐ and Pinane‐Derived Epoxyesters – Coconut Fragrance The base‐induced isomerization of p‐menthane‐ and pinane‐derived epoxy esters was studied. The reaction is dependent on the structure of the terpene compound, the nature of the base, and experimental conditions. Among all the new synthesized compounds, one, 6a , emits a very strong fragrance of coconut. In the structure of this tricyclic lactone, the presence of a methyl substituent is essential.