Selective Transformation of Norbornadiene into Functionalized Azaheterocycles and ß-Amino Esters with Stereo- and Regiocontrol.

Novel functionalized azaheterocycles with multiple chiral centers have been accessed from readily available norbornene ß-amino acids or ß-lactams across a stereocontrolled synthetic route, based on ring-opening metathesis (ROM) of the staring unsaturated bicyclic amino esters, followed by selective cyclization through ring-closing metathesis (RCM). The RCM transformations have been studied under various experimental conditions to assess the scope of conversion, catalyst, yield, and substrate influence. The structure of the starting norbornene ß-amino acids predetermined the structure of the new azaheterocycles, and the developed synthetic route took place with the conservation of the configuration of the chiral centers.

A study on selective transformation of norbornadiene into fluorinated cyclopentane-fused isoxazolines.

This work presents an examination of the selective functionalization of norbornadiene through nitrile oxide 1,3-dipolar cycloaddition/ring-opening metathesis (ROM)/cross-metathesis (CM) protocols. Functionalization of commercially available norbornadiene provided novel bicyclic scaffolds with multiple stereogenic centers. The synthesis involved selective cycloadditions, with subsequent ROM of the formed cycloalkene-fused isoxazoline scaffolds and selective CM by chemodifferentiation of the olefin bonds of the resulting alkenylated derivatives. Various experimental conditions were applied for the CM transformations with the goal of exploring substrate and steric effects, catalyst influence and chemodifferentiation of the olefin bonds furnishing the corresponding functionalized, fluorine-containing isoxazoline derivatives.

Diversity-oriented Functionalization of Cyclodienes Through Selective Cycloaddition/Ring-opening/Cross-metathesis Protocols; Transformation of a "Flatland" into Three-dimensional Scaffolds With Stereo- and Regiocontrol.

This article presents selective transformations of some readily available cyclodienes through simple chemical procedures into novel functionalized small-molecular entities. The syntheses hereby described involved selective cycloadditions, followed by ring-opening metathesis of the resulting ß-lactam or isoxazoline derivatives and selective cross-metathesis by differentiation of the olefin bonds on the alkenylated heterocycles. The cross-metathesis transformations have been detailed, which were performed under various experimental conditions with the aim of exploring chemodiscrimination of the olefin bonds and delivering the corresponding functionalized ß-lactam or isoxazoline derivatives.

Stereocontrolled synthesis of the four possible 3-methoxy and 3-benzyloxy-16-triazolyl-methyl-estra-17-ol hybrids and their antiproliferative activities.

The four possible isomers of each of 3-methoxy- and 3-benzyloxyestra-1,3,5(10)-trien-17-ols (5-8 and 9-12) were converted through 16-p-tosyloxymethyl- or 16-bromomethyl derivatives into their 3-methoxy- and 3-benzyloxy-16-azidomethylestra(1,3,5(10)-triene derivatives (13-16 and 17-20). The regioselective Cu(I)-catalyzed 1,3-dipolar cycloaddition of these compounds with different terminal alkynes afforded novel 1,4-disubstituted diastereomers (21a-f, 22a-f, 23a-f, 24a-f and 25a-f, 26a-f, 27a-f, 28a-f). The antiproliferative activities of the structurally related triazoles were determined in vitro with the microculture tetrazolium assay on four malignant human cell lines of gynecological origin (Hela, SiHa, MCF-7 and MDA-MB-231).

Ring-opening metathesis of some strained bicyclic systems; stereocontrolled access to diolefinated saturated heterocycles with multiple stereogenic centers.

Ring-opening metathesis (ROM) of various unsaturated, constrained bicyclic ring systems has been investigated with the use of commercial ruthenium-based catalysts. Starting from various cyclodienes, the corresponding derived bicyclic lactone, lactam, and isoxazoline derivatives were submitted to ROM under ethenolysis. These functionalized, strained bicyclic systems afforded novel highly-functionalized diolefinated heterocyclic scaffolds in ROM reactions with stereocontrol, through the conservation of the configuration of the stereogenic centers of the starting compounds.

Stereocontrolled synthesis of the four 16-hydroxymethyl-19-nortestosterone isomers and their antiproliferative activities.

Novel 16-hydroxymethyl-19-nortestosterone diastereomers were prepared by Birch reduction from the corresponding 3-methoxy-16-hydroxymethylestra-1,3,5(10)-trien-17-ol isomers with known configurations. The synthesized compounds are 16α- and 16ß-hydroxymethyl-substituted 19-nortestosterone and their 17α-epimers. To prepare 17α-19-nortestosterone, the Mitsunobu inversion reaction of 19-nortestosterone with different alkyl and aryl carboxylic acids was chosen. Deacylation of the new compounds by the Zemplén method yielded the required 17α-19-nortestosterone. The antiproliferative activities of the structurally related compounds were determined in vitro through microculture tetrazolium assays on a panel of human adherent cervical (HeLa, SiHa and C33A), breast (MCF-7, MDA-MB-231, MDA-MB-361 and T47D) and ovarian (A2780) cell lines. The 17α epimer of 19-nortestosterone demonstrated considerable activity, selectively for HeLa cells, with a calculated IC50 of 0.65 µM. The reference compound, cisplatin, displayed an order of magnitude higher IC50 (12.4 µM). The cancer selectivity of 17α-19-nortestosterone was tested by MTT assay performed with noncancerous human fibroblast cell line MRC-5. The results indicated that 17α-19-nortestosterone selectively disturbs the viability of HeLa cells without greatly affecting other cancer cell types and intact fibroblasts.