Antiprotozoal activities of symmetrical bishydroxamic acids

Dimeric Drugs

This review intends to summarize the structures of an extensive number of symmetrical-dimeric drugs, having two monomers linked via a bridging entity while emphasizing the large versatility of biologically active substances reported to possess dimeric structures. The largest number of classes of these compounds consist of anticancer agents, antibiotics/antimicrobials, and anti-AIDS drugs. Other symmetrical-dimeric drugs include antidiabetics, antidepressants, analgesics, anti-inflammatories, drugs for the treatment of Alzheimer's disease, anticholesterolemics, estrogenics, antioxidants, enzyme inhibitors, anti-Parkisonians, laxatives, antiallergy compounds, cannabinoids, etc. Most of the articles reviewed do not compare the activity/potency of the dimers to that of their corresponding monomers. Only in limited cases, various suggestions have been made to justify unexpected higher activity of the dimers vs. the corresponding monomers. These suggestions include statistical effects, the presence of dimeric receptors, binding of a dimer to two receptors simultaneously, and others. It is virtually impossible to predict which dimers will be preferable to their respective monomers, or which linking bridges will lead to the most active compounds. It is expected that the extensive number of articles summarized, and the large variety of substances mentioned, which display various biological activities, should be of interest to many academic and industrial medicinal chemists.

Total syntheses of (+/-)-ovalicin, C4(S *)-isomer, and its C5-analogs and anti-trypanosomal activities

Total syntheses of (+/-)-ovalicin, its C4(S( *))-isomer 44, and C5-side chain intermediate 46 were accomplished via an intramolecular Heck reaction of (Z)-3-(tert-butyldimethylsilyloxy)-1-iodo-1,6-heptadiene and a catalytic amount of palladium acetate. Subsequent epoxidation, dihydroxylation, methylation, and oxidation led to (3S( *),5R( *),6R( *))-5-methoxy-6-(tert-butyldimethylsilyloxy)-1-oxaspiro[2.5]octan-4-one (2), a reported intermediate. The addition of a side chain with cis-1-lithio-1,5-dimethyl-1,4-hexadiene (27) followed by oxidation afforded (+/-)-ovalicin. The functional group manipulation afforded a number of regio- and stereoisomers, which allow the synthesis of analogs for bioevaluation. The structure of 44 was firmly established via a single-crystal X-ray analysis. The stereochemistry at C4 generated from the addition reactions of alkenyllithium with ketones 2, 40, and 45 is dictated by C6-alkoxy functionality. Anti-trypanosomal activities of various ovalicin analogs and synthetic intermediates were evaluated, and C5-side chain analog, 46, shows the strongest activity. Compound 44 shows antiproliferative effect against HL-60 tumor cells in vitro. Compounds 46 and a precursor, (3S( *),4R( *),5R( *),6R( *))-5-methoxy-4-[(E)-(1',5'-dimethylhexa-1',4'-dienyl)]-6-(tert-butyldimethylsilyloxy)-1-oxaspiro[2.5]octan-4-ol (28), may be explored for the development of anti-parasitic drugs.

Oxidation of peptides by methyl(trifluoromethyl)dioxirane: the protecting group matters

Representative Boc-protected and acetyl-protected peptide methyl esters bearing alkyl side chains undergo effective oxidation using methyl(trifluoromethyl)dioxirane (1b) under mild conditions. We observe a protecting group dependency in the chemoselectivity displayed by the dioxirane 1b. N-Hydroxylation occurs in the case of the Boc-protected peptides, and side chain hydroxylation takes place in the case of acetyl-protected peptides. Both are attractive transformations since they yield derivatized peptides that serve as valuable synthons.

A new development of matrix metalloproteinase inhibitors: twin hydroxamic acids as potent inhibitors of MMPs

Starting from the observation that the CbzNH(CH2)2 side chain of the potent MMP-2/MMP-14 inhibitor, benzyl-(3R)-4-(hydroxyamino)-3-[isopropoxy(1,1'-biphenyl-4-yl-sulfonyl)amino]-4-oxobutylcarbamate, (R)-1 lies in a hydrophobic region (S1) exposed to the solvent of the protease active site, we hypothesized that an aminoethylcarboxamido chain structurally related to that of (R)-1 might be an useful tool to bind another linker stretching out from the protein. This would be able to interact either with a enzyme region adjacent to the active site, or with other molecules of matrix metalloproteinases (MMPs), or other proteins of the extracellular matrix (ECM) that may be involved in the enzyme activation. On these basis we describe new dimeric compounds of type 2, twin hydroxamic acids, obtained by the joint of two drug entities of (R)-1 linked in P1 by extendable semirigid linkers. Type 2 compounds are potentially able to undergo more complex inhibitor-enzyme interactions than those occurring with monomeric compounds of type 1, thus influencing positively the potency, selectivity and/or cytotoxicity of the new compounds.