Mini Reviews in Medicinal Chemistry - Volume 3, Issue 4, 2003

Adhesive interactions between molecules expressed on vascular endothelium and circulating tumor cells are key early events in cancer metastasis. Best characterized to date is the selectin family of cell adhesion molecules, which can bind to and stabilize blood-borne cells on organ vasculature, facilitating the cell-cell and cell-substratum interactions leading to tumor seeding and proliferation. Major ligands of E-selectin, the selectin family member expressed on vascular endothelial cells, include sialylated, fucosylated glycans such as Sialyl Lewis type carbohydrate complexes (SLe x and SLe a). These carbohydrate antigens are ubiquitously expressed on tumor cells with high metastatic potential, including colon and pancreatic carcinomas, and have been found to selectively and avidly bind E-selectin.Compounds that prevent E-selectin-SLe x / a binding represent an attractive tool in the prevention of cancer dissemination. Review of preclinical in vitro and in vivo studies suggest that SLe x / a 'mimetics' may serve as a potent class of anti-metastatic compounds. These agents are designed to outcompete SLe x / a antigens expressed on tumor cell surfaces to prevent initial vascular adhesion. Critical in generating exogenous oligosaccharides as SLe x / a mimetics is the stereoselective joining of specific mono- and di- saccharides that express functional groups integral in E-selectin-SLe x / a binding. Employing sulfur linkages to couple saccharide units enhances the biological stability of these complex carbohydrates. The synthesis of novel S-thiodisaccharides and Cdisaccharides as SLe x / a precursors using the chiral sugars levoglucosenone, isomeric isolevoglucosenone and their functionalized analogs is described. The highly stereoselective functionalization of both enones at the C- 4, C-3 and C-2 positions by the set of Michael addition reactions of reactive 1-thiosugars is reviewed. These functionalized S-thio di- and S-oligosaccharide precursors have direct application for use as templates in the synthesis of novel SLe x / a mimetics.

A large series of cyclooxygenase-2 (COX-2) inhibitors with diverse skeletons were investigated by means of the Electronic-Topological Method. A system for the COX-2 inhibitor activity prognostication was built with 6 pharmacophores and 6 anti-pharmacophores. The forecasting ability of the system was also tested on different structures, which differ from those that characterize the series studied.

The role of the corticotropin releasing hormone in the onset of labour and the subsequent medicinal chemistry implications of CRH antagonists for the prevention of premature birth, and identification of the CRH type 1 receptor as the target for this drug design, are reviewed here.

This Review contains our recent studies on evaluation of biological activities associated with monocyclic β-lactams and bicyclic β-lactam antibiotics containing various heteroatoms. A series of bicyclic β-lactams was synthesized, which possessed electron-withdrawing groups, such as an ester, mesylate, and triflate functionality. These β-lactams exhibited enhanced antibacterial activity.

A review is presented on quantitative structure-activity relationships (QSARs) of renin inhibitors which have potential as antihypertensive and cardiovascular agents. They inhibit the renin, an enzyme that is involved in the rate-limiting first step of the renin angiotensin system (RAS). Most of the renin inhibitors are peptidomimetics but recently some nonpeptidomimetic renin inhibitors with low molecular weight have also been developed. In both types of renin inhibitors, the QSARs have exhibited that their inhibition activity would largely depend upon the molecular weight of the compounds, van der waals radius related parameters of the substituents, and the localized electronic effects, particularly of the side chain of the residues substituted in the peptides.

The biological activity of many low molecular weight antitumor compounds appear to be related to their mode and specificity of interaction with particular DNA sequences. Such small molecules are of considerable interest in chemistry, biology and medicine. Most of the anticancer drugs employed clinically exert their antitumor effect by inhibiting nucleic acid (DNA or RNA) or protein synthesis. Inhibition can occur for example through cross-linking of bases in DNA or binding to and inactivation of enzymes necessary for the synthetic processes. It is evident that DNA is an important cellular target for many anticancer agents. Much information has been obtained from molecular genetics, i.e. replication of DNA and its transcription to RNA, which provides the template for protein synthesis. DNA is a well-characterized intracellular target but its large size and sequential nature makes it an elusive target for selective drug action. Binding of low molecular weight ligands to DNA causes a wide variety of potential biological responses. In this context PBDs (pyrrolo[2,1- c][1,4]benzodiazepines), a group of potent naturally occurring antitumor antibiotics produced by various Streptomyces species, are one of the most promising types of lead compounds. They differ in the number, type and position of substituent in both their aromatic A-ring and Py C-rings, and in the degree of saturation of the C-rings which can be either fully saturated or unsaturated at either C2-C3 (endocyclic) or C2 (exocyclic). There is either an imine or carbinolamine methyl ether at the N10-C11 position. This latter is an electrophilic center responsible for alkylating DNA. In the search for compounds with better antitumor selectivity and DNA sequence specificity many PBD analogues have been synthesized in an attempt to increase their potency against tumor cells. We review here recent progress on pyrrolo[2,1-c][1,4]benzodiazepine (PBDs) analogues and their conjugates, also the progress and developments of PBD conjugates with polyamides (information reading molecules in the minor groove of DNA). For example, the cross-linking efficiency of PBD dimers is much greater than that of other cross linkers including cisplatin and melphalan. A large number of PBD dimers and polyamide conjugates with varying linker lengths and bearing different heterocycles at different positions in the PBD ring synthesized in our group and their pharmacological properties have been reviewed.

The chemical diversity and various mechanisms of action of anticonvulsants make it difficult to identify a common pharmacophore. The present review outlines different pharmacophore models for anticonvulsant activity with emphasis on the development of new drugs. Some of them represent models for structurally different classes of compounds with similar mechanisms of action. Others represent pharmacophore models for similar chemical classes of compounds for which the mechanism of anticonvulsant action is not clear. A pharmacophore model for sodium channel blocking compounds, anticonvulsants with the phthalimide pharmacophore, a model for anticonvulsant semicarbazones, and a model for GABA uptake inhibitors are presented.

Hydroxamic acid derivatives are an important class of molecules with a variety of pharmaceutical properties. Over the last decade steady progress has been made in the development of efficient methods for the syntheses of hydroxamic acid derivatives. This mini-review covers the most recent publications that highlight current strategies and syntheses of bioactive molecules containing the hydroxamate moiety in both solutionand solid-phase.

In comparison to the huge number of peptidic and peptidomimetic inhibitors of cysteine proteases which have been developed during the last twenty years the number of non-peptidic compounds with cysteine protease inhibiting properties is restricted to a few substance classes. In contrast to peptidic and peptidomimetic inhibitors the non-peptidic lead structures have mainly been discovered by computational or enzymatic industrial screenings and not by a rational approach. But, the growing number of resolved X-ray structures of the target enzymes as well as molecular modeling methods have supported the further development of potent inhibitors beginning from these lead structures. In this review we will focus on new non-peptidic cysteine protease inhibitors which have been developed during the last years. Discovery, structure-activity-relationship and inhibition mechanisms will be discussed.