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At least 523 records · Page 29Linked to original sources
PubMed2005

Cinchona alkaloid-based polymer-bound phase-transfer catalysts: efficient enantioselective alkylation of benzophenone imine of glycine esters.

Cross-linked polystyrene-bound and poly(ethylene glycol)-bound phase-transfer catalysts as well as homopolymers of cinchona alkaloid derivatives have been synthesised. Both soluble and insoluble polymers have been investigated. The enantioselective alkylation of N-diphenyl methylene glycine t-butyl ester has been successfully carried out in heterogeneous and homogeneous systems. High enantioselectivities (up to 96%) have been obtained. The polymer-bound catalysts have been easily recovered and conditions for efficient recycling have been studied.

Alkylation↗
PubMed1983

Formation of imine derivatives between tris(hydroxymethyl)-aminomethane and saturated 3-oxo steroids during conventional work up of biological samples dissolved in Tris-HCl buffers.

Extraction with organic solvents of Tris-HCl buffer solutions containing microgram amounts of saturated 3-oxo-steroids, followed by evaporation of the organic solvent, produce a condensation product identified as the Tris-3-imino-derivative of the steroid. The yields range between 20-40%. The conditions governing the formation of the derivatives have been explored.

Chemical Phenomena↗
PubMed2005

Quantitative study of the structure-retention index relationship in the imine family.

The Kováts retention index is one of the most popular descriptors of the performance of organic compounds in gas chromatography (GC). The mathematical modeling of this index is an interesting and open problem in analytical chemistry. In this paper, two models for the prediction of the Kováts retention index are presented. Topologic, topographic and quantum-chemical descriptors were used as structural descriptors. Multiple linear regression (MLR) analysis provides the first model using the forward stepwise procedure for the variable selection. For the second one, an ensemble of artificial neural network (ANN) was constructed using the pruning algorithm. Both methods were validated by an external set of compounds, by the Golbraikh and Tropsha method and by the leave-one-out (LOO) and the leave many out (LMO) procedures. The R2, RMScv and Q2, values for the training sets were 0.884, 0.589 and 0.830 for NN and 0.974, 0.417 and 0.970 for MLR models, respectively. The robustness of both models was demonstrated. Both portrait the chromatographic performance of the sample but in this case, the results of MLR equation are better than the NN ones. The MLR model is recommended because of its simplicity.

Imines↗
PubMed1998

Novel (N-ferrocenylmethyl)amines and (N-ferrocenylmethylen)imines derived from vicinal steroid amino alcohols and amines: synthesis, molecular structure, and biological activity.

Novel steroidal (N-ferrocenylmethyl)amines with potential biologic activity and of potential interest as chiral ligands for metal complexation were synthesized. The new compounds were screened in vitro for their potential as antimicrobial agents. The synthesis of the new steroidal ferrocenes, including two X-ray crystal structures and biologic assays, are described. The 16-(ferrocenylmethyl)amino-estratrienes 4a-d, 7b, and 10b exhibited outstanding broad antimicrobial activity particularly against mycobacteria and multi-resistant staphylococci. Thus, they can be considered as new lead structures. In contrast, the analogous 3 alpha-(ferrocenylmethyl)amino-cholestanes 12 possessed only weak activity. The reaction of the four isomeric amino alcohols 1a-d (Scheme 1) with ferrocenecarbaldehyde was studied. 1b and 1c with 16/17-trans configuration yielded nearly quantitatively the (E)-Schiff bases 2b and 2c (Scheme 2). In contrast to the trans-compounds, condensation of the cisconfigurated amino alcohols 1a and 1d furnished tautomeric mixtures of the Schiff bases (2a and 2d, respectively) and their corresponding 1,3-oxazolidines (3a and 3d, respectively). The novel (N-ferrocenylmethyl)amines 4a-d were obtained in excellent yields by reduction of the tautomer mixtures and the uniform Schiff bases with sodium borohydride in ethanol. Starting with the 16 beta-hydroxy compound 5a, the synthesis of 16 beta- and 16 alpha-amino-3-methoxy-estra-1,3,5(10)-triene (6b, 9b) is described. The corresponding 16-(N-ferrocenylmethyl)amines 7b and 10b and the 3 alpha-(N-ferrocenylmethyl)amino-cholestanes 12 were synthesized (Scheme 3) for comparison in biologic tests.

Alcohols↗
PubMed2003

Design and synthesis of orally bioavailable inhibitors of inducible nitric oxide synthase. Identification of 2-azabicyclo[4.1.0]heptan-3-imines.

Further chemical modification of 2-iminopiperidines fused to cyclopropane rings was performed. Optically active isomers 2 and 13 were synthesized and their biological activity was evaluated. Compound 2 exhibited greater potency and more isoform selectivity than enantiomer 13 in the iNOS inhibition assay. One of the gem-chlorines on the fused cyclopropane moiety of 2 was eliminated to produce 3, which showed reduced potency for iNOS inhibition, as well as 4 with an increased potency. The isoform selectivity of 4 was also much higher than that of 3. This was also true for the corresponding methyl derivatives 6-9. The structure-activity relationship (SAR) study and computer aided docking study of the most optimized structure 4 with human iNOS will also be reported.

Animals↗