William A. Kinney

Thrombogenic collagen-mimetic peptides: Self-assembly of triple helix-based fibrils driven by hydrophobic interactions

Collagens are integral structural proteins in animal tissues and play key functional roles in cellular modulation. We sought to discover collagen model peptides (CMPs) that would form triple helices and self-assemble into supramolecular fibrils exhibiting collagen-like biological activity without preorganizing the peptide chains by covalent linkages. This challenging objective was accomplished by placing aromatic groups on the ends of a representative 30-mer CMP, (GPO)10, as with l-phenylalanine and l-pentafluorophenylalanine in 32-mer 1a. Computational studies on homologous 29-mers 1a′–d′ (one less GPO), as pairs of triple helices interacting head-to-tail, yielded stabilization energies in the order 1a′ > 1b′ > 1c′ > 1d′, supporting the hypothesis that hydrophobic aromatic groups can drive CMP self-assembly. Peptides 1a–d were studied comparatively relative to structural properties and ability to stimulate human platelets. Although each 32-mer formed stable triple helices (CD) spectroscopy, only 1a and 1b self-assembled into micrometer-scale fibrils. Light microscopy images for 1a depicted long collagen-like fibrils, whereas images for 1d did not. Atomic force microscopy topographical images indicated that 1a and 1b self-organize into microfibrillar species, whereas 1c and 1d do not. Peptides 1a and 1b induced the aggregation of human blood platelets with a potency similar to type I collagen, whereas 1c was much less effective, and 1d was inactive (EC50 potency: 1a/1b ≫ 1c > 1d). Thus, 1a and 1b spontaneously self-assemble into thrombogenic collagen-mimetic materials because of hydrophobic aromatic interactions provided by the special end-groups. These findings have important implications for the design of biofunctional CMPs.

STEREOSELECTIVE SYNTHESIS OF SQUALAMINE DESSULFATE

Abstract Squalamine dessulfate (24 R ) and the unnatural product squalamine dessulfate (24 S ) have been synthesized from stigmasterol. The key step in establishing the C24 stereochemistry is attachment of the sidechain at C22 using either (2 R )- or (2 S )-1,2-epoxy-3-methylbutane to yield the cholesteryl precursors of the epimeric squalamine dessulfates.

Nonpeptide Urotensin-II Receptor Antagonists: A New Ligand Class Based on Piperazino-Phthalimide and Piperazino-Isoindolinone Subunits

We have discovered two related chemical series of nonpeptide urotensin-II (U-II) receptor antagonists based on piperazino-phthalimide (5 and 6) and piperazino-isoindolinone (7) scaffolds. These structure types are distinctive from those of U-II receptor antagonist series reported in the literature. Antagonist 7a exhibited single-digit nanomolar potency in rat and human cell-based functional assays, as well as strong binding to the human U-II receptor. In advanced pharmacological testing, 7a blocked the effects of U-II in vitro in a rat aortic ring assay and in vivo in a rat ear-flush model. A discussion of U-II receptor antagonist pharmacophores is presented, and a specifically defined model is suggested from tricycle 13, which has a high degree of conformational constraint.

The synthesis of spermine analogs of the shark aminosterol squalamine

Aminosterols isolated from the dogfish shark Squalus acanthias are promising therapeutic agents in the treatment of infection and cancer. One of these, MSI-1436, has been shown to possess antimicrobial activity slightly better than squalamine. In this study, a series of analogs of MSI-1436 have been synthesized from stigmasterol. The 7 alpha-hydroxy substituent of MSI-1436 was either omitted or the stereochemistry modified to the 7 beta position. Also, analogs of MSI-1436 with 24-sulfate, 24-amino, and 24-hydroxy substituents were synthesized in order to assess the importance of the side chain functional group on antimicrobial activity. All of the analogs possess significant antimicrobial activity, suggesting that substitution at C7 and C24 of the aminosterols plays a minor role in their antimicrobial potency.

Urotensin-II Receptor Modulators as Potential Drugs

Amino acidresidues 5-10 of human U-II are contained in a disulfide-linked cyclic array, [CFWKYC], which is highly species-con-served,whereastheN-terminalregionfromotherspeciesdiffersin length and constitution (Figure 1). The first U-II peptide (a12-mer) was isolated from the urophysis of the goby fish(Gillichthys mirabilis) as a smooth muscle contractile sub-stance.

Synthesis of an azido spermidine equivalent

Abstract The synthesis and conversion of a new spermidine equivalent ( 2 ) to squalamine is reported. It is prepared in a practical manner, is stable to sodium borohydride reduction, is converted to spermidine under mild conditions, and is not prone to internal cyclization reactions.

A concise synthesis of an indenopyrrolidine-based dual αvβ3/αvβ5 integrin antagonist

A new class of dual α v β 3 /α v β 5 integrin antagonists containing a central cis-fused cyclopentane ring was identified. Because of its increased structural rigidity, the indenopyrrolidine ring system provides insight intothe active conformation of other α v β 3 ligands. A concise synthesis of the indenopyrrolidine ring system was accomplished by 1,3-dipolar cycloaddition. Individual isomers of the most active compound were separated by chiral HPLC and their biological activities were compared.

The Heck reaction with unprotected allylic amidines and guanidines

The applicability of Heck methodology to the introduction of unprotected amidines and guanidines was investigated. Unprotected guanidine-substituted olefins were coupled to various simple aryl iodides, and this methodology was then applied to a highly functionalized 6-iodoquinazolinone substrate, providing an efficient synthesis of a new class of vitronectin receptor (αVβ3 integrin) antagonists.

Ester Prodrugs of IHVR-19029 with Enhanced Oral Exposure and Prevention of Gastrointestinal Glucosidase Interaction.

IHVR-19029 (6) is a lead endoplasmic reticulum α-glucosidases I and II inhibitor, which efficiently protected mice from lethal Ebola and Marburg virus infections via injection route, but suffered from low bioavailability and off-target interactions with gut glucosidases when administered orally. In an effort to improve efficacious exposure levels and avoid side effects, we designed and synthesized ester prodrugs. Not only were the prodrugs stable in simulated gastric and intestinal fluids and were inactive against glucosidases but they also exhibited antiviral activities against dengue virus infection in a cell based assay. Further in vitro evaluation showed that the bioconversion of the prodrugs is species dependent: in mice, the prodrugs were converted to 6 in the plasma and liver; while in human, the conversion occurred mainly in liver. An in vivo pharmacokinetic study in mice demonstrated that the tetrabutyrate prodrug 8 achieved the most improved overall exposure of 6 upon both oral and intravenous administration.

Novel substituted aminothiazoles as potent and selective anti-hepatocellular carcinoma agents

Based on our previous identification of a disubstituted aminothiazole termed HBF-0079 with promising selective toxicity for HCC-derived cell lines versus non-HCC liver lines, a series of tri-substituted aminothiazole derivatives were prepared and evaluated. This work resulted in the discovery of isopropyl 4-(pyrazin-2-yl)-2-(pyrimidin-2-ylamino)thiazole-5-carboxylate, 14, which displayed EC50 value of 0.11μM and more than 450times of selectivity, and its methyl carbonate prodrug 24 with improved solubility in organic solvents. Furthermore, 14, was shown to reduce the proliferation of several liver cancer cells derived directly from patients.