The potent cytotoxins pederin and psymberin have been prepared through concise synthetic routes (10 and 14 steps in the longest linear sequences, respectively) that proceed via a late-stage multicomponent approach to construct the N-acyl aminal linkages. This route allowed for the facile preparation of a number of analogs that were designed to explore the importance of the alkoxy group in the N-acyl aminal and functional groups in the two major subunits on biological activity. These analogs, including a pederin/psymberin chimera, were analyzed for their growth inhibitory effects, revealing several new potent cytotoxins and leading to postulates regarding the molecular conformational and hydrogen bonding patterns that are required for biological activity. Second generation analogs have been prepared based on the results of the initial assays and a structure-based model for the binding of these compounds to the ribosome. The growth inhibitory properties of these compounds are reported. These studies show the profound role that organic chemistry in general and specifically late-stage multicomponent reactions can play in the development of unique and potent effectors for biological responses.

Plasmodium falciparum, the Apicomplexan parasite that is responsible for the most lethal forms of human malaria, is exposed to radically different environments and stress factors during its complex lifecycle. In any organism, Hsp70 chaperones are typically associated with tolerance to stress. We therefore reasoned that inhibition of P. falciparum Hsp70 chaperones would adversely affect parasite homeostasis. To test this hypothesis, we measured whether pyrimidinone-amides, a new class of Hsp70 modulators, could inhibit the replication of the pathogenic P. falciparum stages in human red blood cells. Nine compounds with IC 50 values from 30 nM to 1.6 μM were identified. Each compound also altered the ATPase activity of purified P. falciparum Hsp70 in single-turnover assays, although higher concentrations of agents were required than was necessary to inhibit P. falciparum replication. Varying effects of these compounds on Hsp70s from other organisms were also observed. Together, our data indicate that pyrimidinone-amides constitute a novel class of anti-malarial agents.

(-)-Dictyostatin is a sponge-derived, 22-member macrolactone natural product shown to cause cells to accumulate in the G2/M phase of the cell cycle, with changes in intracellular microtubules analogous to those observed with paclitaxel treatment. Dictyostatin also induces assembly of purified tubulin more rapidly than does paclitaxel, and nearly as vigorously as does dictyostatin's close structural congener, (+)-discodermolide (Isbrucker et al. (2003), Biochem. Pharmacol. 65, 75-82). We used synthetic (-)-dictyostatin to study its biochemical and cytological activities in greater detail. The antiproliferative activity of dictyostatin did not differ greatly from that of paclitaxel or discodermolide. Like discodermolide, dictyostatin retained antiproliferative activity against human ovarian carcinoma cells resistant to paclitaxel due to beta-tubulin mutations and caused conversion of cellular soluble tubulin pools to microtubules. Detailed comparison of the abilities of dictyostatin and discodermolide to induce tubulin assembly demonstrated that the compounds had similar potencies. Dictyostatin inhibited the binding of radiolabeled discodermolide to microtubules more potently than any other compound examined, and dictyostatin and discodermolide had equivalent activity as inhibitors of the binding of both radiolabeled epothilone B and paclitaxel to microtubules. These results are consistent with the idea that the macrocyclic structure of dictyostatin represents the template for the bioactive conformation of discodermolide.

Facile syntheses of C-6 azidopurine ribonucleosides and 2′-deoxyribonucleosides have been developed. For silyl and acetyl protected as well as unprotected nucleosides, access to the azido derivatives could be readily attained via displacement of BtO − from the O 6 -(benzotriazol-1-yl) inosine nucleosides by azide anion. Use of diphenylphosphoryl azide/DBU as a simple route to the acetyl-protected azido nucleosides was also evaluated, but this proved to be inferior. Since these azido nucleosides can exist in an azide•tetrazole equilibrium, the effect of solvent polarity on this equilibrium was investigated. Subsequently, a detailed analysis of Cu-mediated azide-alkyne ("click") ligation was undertaken. Biphasic CH 2 Cl 2 /H 2 O medium proved to be best for the ligation reactions, suppressing the undesired azide reduction that was competing. Interestingly, although the tetrazolyl isomer predominates (ca 80%) in CD 2 Cl 2 and in CD 2 Cl 2 /D 2 O, the Cu-catalyzed click reactions proceed smoothly with the silyl-protected ribo and 2′-deoxyribonucleosides, leading to the C-6 triazolyl products in good to excellent yields. Thus, depletion of azido form from the reaction mixture shifts the azide•tetrazole equilibrium, eventually resulting in complete consumption of azide and tetrazole. In several cases, major and minor azide-alkyne ligation products were observed and characterization data are provided for both. In order to confirm the regiochemistry leading to the major isomer, one product was crystallized and evaluated by X-ray crystallography. The Cucatalyzed azide-alkyne ligation is clearly efficient and significantly superior to thermal reactions, which were slow. Biological evaluation showed low cytotoxicities for the agents, suggesting their usefulness as biological probes.* To whom correspondence should be addressed. Tel.: (212) 650-7835; fax: (212) 650-6107. lakshman@sci.ccny.cuny.edu. Supporting Information Available: General experimental details, materials and methods for antiproliferative tests and the results, ORTEP of 4b, copies of 1 H and 13 C NMR spectra of 2c, 2d, 3a-f, 4a-g, 4f′, 5a-g, 5a′, 5c′-f′, 6a-6g and 7a-7g. This information is available free of charge via the Internet at

The dictyostatins are a promising class of potential anticancer drugs because they are powerful microtubule stabilizing agents, but the complexity of their chemical structures is a severe impediment to their further development. Based on both synthetic and medicinal chemistry analyses, 25,26-dihydro-16-desmethyldictyostatin and its C6 epimer were chosen as potentially potent yet accessible dictyostatin analogs, and three new syntheses were developed. A relatively classical synthesis involving vinyllithium addition and macrocyclization gave way to a newer and more practical approach based on esterification and ring-closing metathesis reaction. Finally, aspects of these two approaches were combined to provide a third new synthesis based on esterification and Nozaki-Hiyama-Kishi reaction. This was used to prepare the target dihydro analogs and the natural product. All of the syntheses are streamlined because of their high convergence. The work provided several new analogs of dictyostatin including a truncated macrolactone and a C10 E-alkene, which were 400-fold and 50-fold less active than (−)-dictyostatin. In contrast, the targeted 25,26-dihydro-16-desmethyldictyostatin analogs retained almost complete activity in preliminary biological assays.

Salmonella bacteria cause millions of infections and thousands of deaths every year. This pathogen has an unusually broad host range including humans, animals, and even plants. During infection, Salmonella expresses a variety of virulence factors and effectors that are delivered into the host cell triggering cellular responses through protein–protein interactions (PPIs) with host cell proteins which make the pathogen’s invasion and replication possible. To speed up proteomic efforts in elucidating Salmonella–host interactomes, we carried out a survey of the currently published Salmonella–host PPI. Such a list can serve as the gold standard for computational models aimed at predicting Salmonella–host interactomes through integration of large-scale biological data sources. Manual literature and database search of >2200 journal articles and >100 databases resulted in a gold standard list of currently 62 PPI, including primarily interactions of Salmonella proteins with human and mouse proteins. Only six of these interactions were directly retrievable from PPI databases and 16 were highlighted in databases featuring literature extracts. Thus, the literature survey resulted in the most complete interactome available to date for Salmonella. Pathway analysis using Ingenuity and Broad Gene Set Enrichment Analysis (GSEA) software revealed among general pathways such as MAPK signaling in particular those related to cell death as well as cell morphology, turnover, and interactions, in addition to response to not only Salmonella but also other pathogenic – viral and bacterial – infections. The list of interactions is available at http://www.shiprec.org/indicationslist.htm

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The synthesis and biological evaluation of three tubulysin analogs provides the first structure-activity relationship in this family of potent cytotoxic myxobacteria metabolites. Most importantly, the labile N,O-acetal at N(14) is not essential for biological activity. Further, structural simplifications are possible without abolishing biological activities. The N-terminal amino acid can be replaced with N-methylsarcosine, and the configuration at the acetoxy-bearing stereocenter at C(11) is important but not critical for almost all aspects of the biological profile. Our data encourage further development of these compounds as potential therapeutic agents in cancer treatment.