Transition Metal-Catalyzed C-H Oxidation of Saturated Hydrocarbons with Molecular Oxygen

The C-H oxidation of saturated hydrocarbons to the corresponding alcohols and ketones can be performed efficiently at room temperature with molecular oxygen (1 atm) in the presence of acetaldehyde and catalysts such as Fe, Cu(OH)₂ , and CuCl₂ -18-crown-6 complex. Moreover, extremely high turnover numbers (>27,000) have been obtained for the C-H oxidation of saturated hydrocarbons with molecular oxygen (1 atm) using a combination of Cu(OAc)₂ and acetonitrile at 70 °C. Related oxidation reactions such as epoxidation, Baeyer-Villiger reaction, acetoxylation of β-lactams with molecular oxygen and a suitable aldehyde at room temperature are described.

Oxidative Amide Coupling from Functionally Diverse Alcohols and Amines Using Aerobic Copper/Nitroxyl Catalysis

The aerobic Cu/ABNO catalyzed oxidative coupling of alcohols and amines is highlighted in the synthesis of amide bonds in diverse drug-like molecules (ABNO=9-azabicyclo[3.3.1]nonane N-oxyl). The robust method leverages the privileged reactivity of alcohols bearing electronegative hetero- atoms (O, F, N, Cl) in the β-position. The reaction tolerates over 20 unique functional groups and is demonstrated on a 15 mmol scale under air. Steric constraints of the catalyst allow for chemoselective amidation of primary amines in the presence of secondary amines. All catalyst components are commercially available, and the reaction proceeds under mild conditions with retention of stereocenters in both reaction partners, while producing only water as a by-product.

Highly selective acylation of polyamines and aminoglycosides by 5-acyl-5-phenyl-1,5-dihydro-4H-pyrazol-4-ones

5-Acyl-5-phenyl-1,5-dihydro-4H-pyrazol-4-ones, accessible from arylpropargyl phenyldiazoacetates, are highly selective acyl transfer reagents for di- and polyamines, as well as aminoalcohols and aminothiols. As reagents with a carbon-based leaving group, they have been applied for benzoyl transfer with a broad selection of substrates containing aliphatic amino in combination with other competing nucleophilic functional groups. The substrate scope and levels of selectivity for direct benzoyl transfer exceed those of known benzoylating reagents. With exceptional selectivity for acylation between primary amines bound to primary and secondary carbons, these new reagents have been used in direct site-selective monobenzoylation of aminoglycoside antibiotics.

A nanotechnology-based analog of monoclonal antibodies for targeted delivery of diagnostic and therapeutic agents

The goal of our research is in vivo molecular and cellular imaging. This includes but is not limited to the imaging of protein expression. Dendrimers are an extremely monodisperse polymer used in many types of targeted delivery. Dendrimer families currently used have only one type of surface functional group. Thus when adding both targeting and reporter molecules one gets an ensemble of dendrimer based agents with different avidities. This is analogous to the production of polyclonal antibodies which are a solution of different proteins that bind to the same target with different affinities, and avidities. Using tris-ester protected acids and alpha,omega-protected triamine building blocks we created a dendrimer family with two or more different types of surface functional groups and different protecting groups. This framework technology allows the independent and quantitative addition of targeting, reporter, and/or therapeutic molecules. This provides a solution of identical molecules all with the same avidity and affinity for the target, much like monoclonal antibodies.

Synthesis of α-keto esters by the rhodium-catalysed reaction of cyanoformate with arylboronic acids

An arylrhodium(I) species selectively reacts with the cyano group of ethyl cyanoformate to afford the corresponding alpha-keto ester in good yield.

Synthesis and analgesic activity of a series of new azaalkane bis-guanidinium and bis(2-aminoimidazolinium) compounds

In the present paper, we wish to report the synthesis and antinociceptive activity of a series of new azaalkane bis(2-aminoimidazolinium) compounds from which, N,N'-di(4,5-dihydro-1H-imidazol-2-yl)-3-aza-1,6-hexanediamine 2a has shown the best analgesic properties in vivo in two different assays (i.e., acetic acid-induced writhing test and hot-plate test in mice), as well as oral bioavailability.

Novel Dendritic alpha-Sialosides: Synthesis of Glycodendrimers Based on a 3,3'-Iminobis(propylamine) Core

The cluster or multivalent effect has been recognized as an effective means by which to increase binding interactions between carbohydrates and proteins. In fact, it has been demonstrated that sialylated multibranched L-lysine dendrimers were potent inhibitors of hemagglutination of human erythrocytes by Influenza viruses. In a continuation of these studies, the synthesis of novel glycodendrimers with even valencies from 2 to 16 and ending with equidistant thiosialoside residues is described. These symmetrical dendrimers were more readily characterized by standard NMR spectral techniques than previously reported nonsymmetrical dendrimers of this general type. The synthesis of the dendritic core was based on the regioselective protection of the primary amines of 3,3'-iminobis(propylamine) (4) using benzyl cyanoformate. The resulting secondary amine 5 was alkylated with tert-butyl bromoacetate to provide divalent core structure 6 with Cbz protected amines and acid protected tert-butyl ester. Sequential deprotection by trifluoroacetolysis or hydrogenation afforded acid 7 or diamine 8 as key precursors, respectively. The two fragments were coupled using HOBt/DIC strategy to provide Cbz-protected dendrimers with valencies of 2, 4, 8, and 16 in the first, second, third, and fourth generations, respectively, in reasonable to good yields (42-82%). Cbz-protected precursors were efficiently transformed into N-chloroacetylated dendrimers by hydrogenolysis and treatment of the resulting amines with chloroacetic anhydride (82-91%). N-Chloroacetylated dendrimers were then treated with an excess of 2-thiosialic acid derivative 3 to give fully protected sialodendrimers in 76-96% yields. Deprotection of sialodendrimers under Zemplén conditions followed by methyl ester saponification and purification by gel permeation chromatography afforded symmetrical dendritic alpha-thiosialosides 21, 23, 25, and 27 in fair yields (47-58%). These novel sialodendrimers, in keeping with their design, are currently being evaluated as inhibitors of human erythrocyte hemagglutination by Influenza viruses.

Inhibiting effects of spermidine derivatives on Trypanosoma cruzi trypanothione reductase

Trypanothione reductase is a vital component of the antioxidant defenses of trypanosomes. This enzyme reduces trypanothione, a spermidine-glutathione conjugate. The inhibitory effects of several spermidine derivatives on the reduction of trypanothione by Trypanosoma cruzi trypanothione reductase were assessed. Spermidine derivatives containing hydrophobic aromatic substituents were found to be competitive inhibitors of trypanothione reductase. N4-acylated spermidine derivatives were less effective inhibitors than the corresponding N4-alkylated derivatives. The most effective compounds studied were N1, N8-bis(2-naphthylmethyl)spermidine and N4-(2-naphthylmethyl)spermidine, with Ki values of 9.5 and 108 microM, respectively.