Ultrapotent vinblastines in which added molecular complexity further disrupts the target tubulin dimer-dimer interface.

Approaches to improving the biological properties of natural products typically strive to modify their structures to identify the essential pharmacophore, or make functional group changes to improve biological target affinity or functional activity, change physical properties, enhance stability, or introduce conformational constraints. Aside from accessible semisynthetic modifications of existing functional groups, rarely does one consider using chemical synthesis to add molecular complexity to the natural product. In part, this may be attributed to the added challenge intrinsic in the synthesis of an even more complex compound. Herein, we report synthetically derived, structurally more complex vinblastines inaccessible from the natural product itself that are a stunning 100-fold more active (IC50 values, 50-75 pM vs. 7 nM; HCT116), and that are now accessible because of advances in the total synthesis of the natural product. The newly discovered ultrapotent vinblastines, which may look highly unusual upon first inspection, bind tubulin with much higher affinity and likely further disrupt the tubulin head-to-tail α/ß dimer-dimer interaction by virtue of the strategic placement of an added conformationally well-defined, rigid, and extended C20' urea along the adjacent continuing protein-protein interface. In this case, the added molecular complexity was used to markedly enhance target binding and functional biological activity (100-fold), and likely represents a general approach to improving the properties of other natural products targeting a protein-protein interaction.

Design of Benzoxathiazin-3-one 1,1-Dioxides as a New Class of Irreversible Serine Hydrolase Inhibitors: Discovery of a Uniquely Selective PNPLA4 Inhibitor.

The design and examination of 4,1,2-benzoxathiazin-3-one 1,1-dioxides as candidate serine hydrolase inhibitors are disclosed, and represent the synthesis and study of a previously unexplored heterocycle. This new class of activated cyclic carbamates provided selective irreversible inhibition of a small subset of serine hydrolases without release of a leaving group, does not covalently modify active site catalytic cysteine and lysine residues of other enzyme classes, and was found to be amenable to predictable structural modifications that modulate intrinsic reactivity or active site recognition. Even more remarkable and within the small pilot series of candidate inhibitors examined in an initial study, an exquisitely selective inhibitor for a poorly characterized serine hydrolase (PNPLA4, patatin-like phospholipase domain-containing protein 4) involved in adipocyte triglyceride homeostasis was discovered.

Synthesis of a Potent Vinblastine: Rationally Designed Added Benign Complexity.

Many natural products, including vinblastine, have not been easily subjected to simplifications in their structures by synthetic means or modifications by late-stage semisynthetic derivatization in ways that enhance their biological potency. Herein, we detail a synthetic vinblastine that incorporates added benign complexity (ABC), which improves activity 10-fold, and is now accessible as a result of advances in the total synthesis of the natural product. The compound incorporates designed added molecular complexity but no new functional groups and maintains all existing structural and conformational features of the natural product. It constitutes a member of an analogue class presently inaccessible by semisynthetic derivatization of the natural product, by its late-stage functionalization, or by biosynthetic means. Rather, it was accessed by synthetic means, using an appropriately modified powerful penultimate single-step vindoline-catharanthine coupling strategy that proceeds with a higher diastereoselectivity than found for the natural product itself.

Synthesis and evaluation of duocarmycin SA analogs incorporating the methyl 1,2,8,8a-tetrahydrocyclopropa[c]imidazolo[4,5-e]indol-4-one-6-carboxylate (CImI) alkylation subunit.

The design, synthesis, and evaluation of methyl 1,2,8,8a-tetrahydrocyclopropa[c]imidazolo[4,5-e]indol-4-one-6-carboxylate (CImI) derivatives are detailed representing analogs of duocarmycin SA and yatakemycin containing an imidazole replacement for the fused pyrrole found in the DNA alkylation subunit.

A five-membered lactone prodrug of CBI-based analogs of the duocarmycins.

The preparation, characterization and examination of the CBI-based 5-membered lactone 5 capable of serving as a prodrug or protein (antibody) conjugation reagent are disclosed along with its incorporation into the corresponding CC-1065 and duocarmycin analog 6, and the establishment of their properties.

Inhibition of carcinoma cell motility by epoxyeicosatrienoic acid (EET) antagonists.

Cytochrome P450 (CYP) epoxygenases, CYP2C8, 2C9 and 2J2 mRNA and proteins, were expressed in prostate carcinoma (PC-3, DU-145 and LNCaP) cells. 11,12-Epoxyeicosatrienoic acid (11,12-EET) was the major arachidonic acid metabolite in these cells. Blocking EET synthesis by a selective CYP epoxygenase inhibitor (N-methylsulfonyl-6-(2-propargyloxyphenyl)hexanamide [MS-PPOH]) inhibited tonic (basal) invasion and migration (motility) while exogenously added EET induced cell motility in a concentration-dependent manner. An epidermal growth factor receptor (EGFR) kinase inhibitor (AG494) or a PI3 kinase inhibitor (LY294002) inhibited cell migration and reduced 11,12-EET-induced cell migration. Importantly, synthetic EET antagonists (14,15-epoxyeicosa-5(Z)-enoic acid [14,15-EEZE], 14,15-epoxyeicosa-5(Z)-enoic acid 2-[2-(3-hydroxy-propoxy)-ethoxy]-ethyl ester [14,15-EEZE-PEG] and 14,15-epoxyeicosa-5(Z)-enoic-methylsulfonylimide [14,15-EEZE-mSI]) inhibited EET-induced cell invasion and migration. 11,12-EET induced cell stretching and myosin-actin microfilament formation as well as increased phosphorylation of EGFR and Akt (Ser473), while 14,15-EEZE inhibited these effects. These results suggest that EET induce and EET antagonists inhibit cell motility, possibly by putative EET receptor-mediated EGFR and PI3K/Akt pathways, and suggest that EET antagonists are potential therapeutic agents for prostate cancer.

Total synthesis of a key series of vinblastines modified at C4 that define the importance and surprising trends in activity.

The total synthesis and evaluation of a key systematic series of vinblastines that incorporate the first deep-seated changes to the substituent at C4 are detailed. The synthetic approach features an expanded and redefined scope of a 1,3,4-oxadiazole [4 + 2]/[3 + 2] cycloaddition cascade in which electronically mismatched electron-deficient trisubstituted alkenes and unactivated trisubstituted alkenes were found to productively initiate the cycloaddition cascade with tethered electron-deficient 1,3,4-oxadiazoles. Such cycloaddition cascades were used to directly introduce altered C4 substituents, providing the basis for concise total syntheses of a series of C4 modified vindolines and their subsequent single-step incorporation into the corresponding synthetic vinblastines in routes as short as 8-12 steps. Evaluation of the synthetic vinblastines revealed a surprisingly large impact and role of the C4 substituent on activity even though it was previously not thought to intimately interact with the biological target tubulin. Only the introduction of a C4 methyl ester, a constitutional isomer of vinblastine in which the carbonyl carbon and ester oxygen of the C4 acetate are transposed, provided a synthetic vinblastine that matched the potency of the natural product. In contrast, even introduction of a C4 acetamide or N-methyl carboxamide, which incorporate single heavy atom exchanges (amide NH for ester oxygen) in vinblastine or the C4 methyl ester, provided compounds that were ≥10-fold less active than vinblastine. Other C4 acetate replacements, including a C4 amine, carboxylic acid, hydroxymethyl or acetoxymethyl group, led to even greater reductions in potency. Even replacement of the C4 acetoxy group or its equally active C4 methyl ester with an ethyl or isopropyl ester led to 10-fold or more reductions in activity. These remarkable trends in activity, which correlate with relative tubulin binding affinities, retrospectively may be ascribed to the role the substituent serves as a H-bond acceptor for α-tubulin Lys336 and Asn329 side chains at a site less tolerant of a H-bond donor, placing the methyl group of the C4 acetate or C4 methyl ester in a spatially restricted and well-defined hydrophobic half pocket created by a surrounding well-ordered loop. This remarkable impact of the C4 substituent, its stringency, and even the magnitude of its effect are extraordinary, and indicate that its presence was selected in Nature to enhance the effects of vinblastine and related natural products.

Vinblastine 20' Amides: Synthetic Analogues That Maintain or Improve Potency and Simultaneously Overcome Pgp-Derived Efflux and Resistance.

A series of 180 vinblastine 20' amides were prepared in three steps from commercially available starting materials, systematically exploring a typically inaccessible site in the molecule enlisting a powerful functionalization strategy. Clear structure-activity relationships and a structural model were developed in the studies which provided many such 20' amides that exhibit substantial and some even remarkable enhancements in potency, many that exhibit further improvements in activity against a Pgp overexpressing resistant cancer cell line, and an important subset of the vinblastine analogues that display little or no differential in activity against a matched pair of vinblastine sensitive and resistant (Pgp overexpressing) cell lines. The improvements in potency directly correlated with target tubulin binding affinity, and the reduction in differential functional activity against the sensitive and Pgp overexpressing resistant cell lines was found to correlate directly with an impact on Pgp-derived efflux.

A practical synthesis of bridged diarylacetylenes.

An efficient and practical synthesis of bridged diarylacetylenes in multigram quantities has been successfully carried out using high-yielding (classical) synthetic methods and readily available starting materials. The structural analysis of the representative bridged diarylacetylenes by X-ray crystallography strongly suggests that conformations, bending of the linear triple bond, and the angle between the mean planes of aromatic rings in various bridged diarylacetylenes are governed by the p-pi conjugation among the aromatic rings and the ethereal groups. Furthermore, the synthetic scheme also allows the preparation of (appropriately) bromo-substituted bridged diarylacetylenes which hold potential for their future usage for the preparation of polymeric analogues as well as the hexaarylbenzene derivatives for potential applications in the emerging area of molecular electronics and nanotechnology.