Preliminary SAR analysis of novel antiproliferative N(6),5'-bis-ureidoadenosine derivatives.

A preliminary library of novel N(6),5'-bis-ureidoadenosine analogs and related derivatives was prepared and tested for activity against the NCI 60 panel of human cancers. A 2'-O-TBS group was found to be necessary, but not sufficient, for optimal antiproliferative activity. Neither the N(6)- nor 5'-ureido substituents were sufficient to achieve significant antiproliferative effects when present in the absence of the other. The 2'-O-TBS, and N(6),5'-bis-ureido substitution patterns were found to be necessary for optimal antiproliferative activity.

Phase-transfer-catalyzed asymmetric acylimidazole alkylation.

2-Acylimidazoles are alkylated under phase-transfer conditions with cinchonidinium catalysts at -40 degrees C with allyl and benzyl electrophiles in high yield with excellent enantioselectivity (79 to >99% ee). The acylimidazole substrates are made in three steps from bromoacetic acid via the N-acylmorpholine adduct. The catalyst is made in high purity allowing for S-product formation (6-20 h) under mild conditions, consistent with an ion-pair mechanism. The products are readily converted to useful ester products using methyltriflate and sodium methoxide, via a dimethylacylimidazolium intermediate without racemization. The process is efficient, direct, and amenable to other electrophiles and transformations that proceed through an enolate intermediate.

Meta-omic characterization of the marine invertebrate microbial consortium that produces the chemotherapeutic natural product ET-743.

In many macroorganisms, the ultimate source of potent biologically active natural products has remained elusive due to an inability to identify and culture the producing symbiotic microorganisms. As a model system for developing a meta-omic approach to identify and characterize natural product pathways from invertebrate-derived microbial consortia, we chose to investigate the ET-743 (Yondelis) biosynthetic pathway. This molecule is an approved anticancer agent obtained in low abundance (10(-4)-10(-5) % w/w) from the tunicate Ecteinascidia turbinata and is generated in suitable quantities for clinical use by a lengthy semisynthetic process. On the basis of structural similarities to three bacterial secondary metabolites, we hypothesized that ET-743 is the product of a marine bacterial symbiont. Using metagenomic sequencing of total DNA from the tunicate/microbial consortium, we targeted and assembled a 35 kb contig containing 25 genes that comprise the core of the NRPS biosynthetic pathway for this valuable anticancer agent. Rigorous sequence analysis based on codon usage of two large unlinked contigs suggests that Candidatus Endoecteinascidia frumentensis produces the ET-743 metabolite. Subsequent metaproteomic analysis confirmed expression of three key biosynthetic proteins. Moreover, the predicted activity of an enzyme for assembly of the tetrahydroisoquinoline core of ET-743 was verified in vitro. This work provides a foundation for direct production of the drug and new analogues through metabolic engineering. We expect that the interdisciplinary approach described is applicable to diverse host-symbiont systems that generate valuable natural products for drug discovery and development.

Antiproliferative and protein kinase binding activities of Some N6, 5'-bis-ureido 5'-amino-5'-deoxyadenosine derivatives.

Two novel N(6),5'-bis-ureido 5'-amino-5'-deoxyadenosine derivatives are shown to inhibit tumor cell growth in the NCI 60 human tumor cell panel. Compounds 2c and 2d exhibited GI(50) values of 1-6 microM in 35 and 14 cell lines, respectively. Compound 2c was shown to selectively inhibit binding of protein kinases to immobilized ATP-binding site ligands via a competitive binding assay (11 of 353 protein kinases inhibited by > or =30% at 10 microM compound concentration). Enzyme inhibition assays revealed modest inhibition for PAK4 and FMS (21 and 17%, respectively). A brief SAR study suggests that a 2'-O-TBDMS is necessary for antiproliferative activity.