Key words sultams - spirocycles - sulfonyl fluorides - azetidines - pyrrolidines - piperidines

The reagent di-tert-butyl ethynylimidodicarbonate is demonstrated as a β-aminoethyl anion synthetic equivalent. It can be used to install ethyleneamine groups by exploiting its terminal alkyne reactivity with common organic electrophiles. Reactions exemplified with this terminal ynimide reagent include additions to imines, aldehydes, ketones, pyridinium salts, Michael acceptors, epoxides, and Pd-catalyzed Sonogashira couplings. Subsequent regioselective [3 + 2] cycloadditions of the alkynyl-imides (ynimides) generate N,N-di-Boc imide-functionalized triazole and isoxazole heterocycles. Reduction of the ynimides with Pd-catalyzed hydrogenation generates ethyleneimides with easily removable N,N-di-Boc-carbamate protecting groups, allowing for a flexible ynimide-based approach to ethyleneamine installation. The utility of this two-step aminoethylation strategy was demonstrated in the short formal syntheses of pyrrolidinoindoline alkaloids (±)-CPC-1 and (±)-alline. Analogously, the reagent (N,N,N')-tri-Boc 2-ethynylhydrazine serves as a β-hydrazinoethyl anion synthetic equivalent.

Several polar heteroaromatic acetic acids and their piperidine amides were synthesized and evaluated as ghrelin or type 1a growth hormone secretagogue receptor (GHS-R1a) inverse agonists. Efforts to improve pharmacokinetic and safety profile was achieved by modulating physicochemical properties and, more specifically, emphasizing increased polarity of our chemical series. ortho-Carboxamide containing compounds provided optimal physicochemical, pharmacologic, and safety profile. pH-dependent chemical stability was also assessed with our series.

The total syntheses of the highly cytotoxic neo-antimycin macrocyclic depsipeptide natural products kitastatin and respirantin have been accomplished in a convergent manner using MNBA promoted esterifications and an efficient C- and N-terminus bis-deprotection/HATU promoted macrolactamization. The first examples of using a prenyltrifluoroborate reagent in additions to carbonyl groups are disclosed including a diastereoselective multigram scale montmorillonite K10 catalyzed prenylation of N-Boc-l-leucinal to install the structurally unique gem-dimethyl-β-keto-ester fragment.

The identification of potent, highly selective orally bioavailable ghrelin receptor inverse agonists from a spiro-azetidino-piperidine series is described. Examples from this series have promising in vivo pharmacokinetics and increase glucose-stimulated insulin secretion in human whole and dispersed islets. A physicochemistry-based strategy to increase lipophilic efficiency for ghrelin receptor potency and retain low clearance and satisfactory permeability while reducing off-target pharmacology led to the discovery of 16h. Compound 16h has a superior balance of ghrelin receptor pharmacology and off-target selectivity. On the basis of its promising pharmacological and safety profile, 16h was advanced to human clinical trials.

The first total syntheses of two natural antitumor enehydrazide compounds (hydrazidomycins A and B) and a related positional isomer of hydrazidomycin B (elaiomycin B) have been accomplished in a rapid and stereocontrolled fashion using a Peterson elimination approach. A regioselective silyl epoxide ring opening reaction with Boc-carbazate followed by base-mediated Peterson siloxide elimination stereospecifically installed the key Z-enehydrazide functionality. The use of Boc-carbazate allowed for the differential functionalization of the hydrazide nitrogens.

In the context of our ghrelin inverse agonist program, a functionalized bromoindane 3 provided a versatile intermediate for structure–activity relationship studies. After developing operationally simple cross-coupling reactions, a broad spectrum of chemical space was successfully explored. Optimization of a one-pot borylation/Suzuki sequence provided the desired products in high yield with low loading of the palladium catalyst. High yields of N-linked heterocyclic analogues were obtained through palladium catalyzed C–N bond formation. In addition, carboxylation of the bromoindane provided an indane carboxylic acid for further diversification.

A convenient route to prepare azaindoles and related pyrrolo-fused heterocycles from boronic acids, DBAD (di-tert-butyl-diazodicarboxylate) and enolizable aldehydes and ketones is presented. The reaction proceeds via a one-pot four-step cascade sequence with key steps involving a copper-catalyzed boronic acid coupling to DBAD and a Fischer indolization providing access to a variety of pharmaceutically interesting heterocycles including pyrrolo-pyridines, -pyrimidines, -quinolines, and -isoquinolines from readily available aza-aryl boronic acid precursors. (C) 2011 Elsevier Ltd. All rights reserved.

A new route to form C(sp)-N bonds has been developed via addition of in situ generated lithium acetylides to sterically hindered diazodicarboxylates. The reaction provides straightforward access to a previously unexplored ynehydrazide class of stable N-linked alkynes directly from commercially available precursors. Preliminary results show that alkynyl hydrazides are useful reagents for the selective installation of nitrogen functional groups and as precursors to pharmaceutically relevant heterocycles using metal catalyzed cycloadditions and condensations.

AbstractA new and widely applicable access to the title compounds is reported.

Pharmacological characterization of receptors at the species level is important in drug discovery to evaluate efficacy and safety. When using an animal model to evaluate efficacy and safety the pharmacological profile of the compounds in the animal species must align with the human pharmacological profile in order to interpret the data correctly. Differences in pharmacological profiles between ovine and human MT1 receptors as well as rat and human MT1 and MT2 receptors have been reported. Therefore, in this study we evaluated a panel of known MT1 and MT2 ligands for binding affinity and function against human, monkey and rat MT1 and MT2 receptors. Human, monkey and rat MT1 and MT2 receptor recombinately expressing cell lines were developed using the Invitrogen CHO‐FLP‐IN TREX system. Several melatonin ligands were characterized in binding assays using human, monkey and rat MT1 and MT2 expressing cell membranes and 2‐[125I]‐iodomelatonin. Functionality of the ligands were evaluated in [35S]‐GTP‐[gamma]‐binding assays in agonist and antagonist mode. Differences in binding affinity and functionality between human and rat receptors were observed but no differences between human and monkey were observed. Therefore, species differences in the pharmacology will have an impact on interpretation of the efficacy and safety data.

The syntheses, characterisation and biological activities (IC50; DNA binding) of four mononuclear Pt oxazoline complexes are reported. These materials are the compounds cis-[PtCl2(NH3)(Etox-κ1N)] (1: Etox = 2-ethyl-2-oxazoline), [PtCl2(anilox-κ2N,N′)] (2: anilox = 4,4-dimethyl-2-[o-anilinyl]-2-oxazoline), cis-[PtCl2(Etox-κ1N)2] (3) and [PtCl(pyox-κ3N,N′,N′)] (4: pyoxH = pyridine-2-carboxyanil-[o-{4,4-dimethyl-2-oxazolinyl}-ide]) and all four are shown to have slightly lower cytotoxicities in vitro when compared to cisplatin against the A2780 ovarian cancer cell line. These new materials all appear to be bio-active via the formation of DNA adducts. Complexes 1 and 2 have been further characterised in the solid-state by X-ray diffraction methods.

A mild, copper-catalyzed coupling of organoindium reagents with nitrogen-containing aromatic heterocycles and chloroformates is described. This reaction proceeds with a range of organoindium reagents, yielding predominately or exclusively the 1,4-addition products with pyridine. In addition, a range of other nitrogen-containing heterocycles can be employed in this reaction (e.g. benzoxazole, benzothiazole, phthalazine). As an illustration of the utility of this reaction, this heterocycle functionalization is coupled with a subsequent oxidation to achieve the one-pot synthesis of functionalized pyridine and benzothiazole derivatives.

A one-pot, copper-catalyzed method to construct 2-alkynylpyridines is presented. This provides a route to access these products directly from terminal alkynes and the parent pyridine, and without prefunctionalization of the pyridine core. In addition, (Z)-alk-2-enylpyridines can be prepared via a related procedure. These reactions are used to synthesize a number of new alkynyl- and alkenyl-substituted pyridines in one pot.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A straight-forward route to prepare a diverse set of N-aryl pyrazoles via a one-pot copper-catalyzed boronic acid coupling and cyclization protocol is presented. A variety of aryl and heteroaryl N-functionalized pyrazoles not easily accessible by other means were formed in good yield from readily available boronic acid precursors in an operationally simple procedure. (C) 2010 Elsevier Ltd. All rights reserved.

A copper (I)-catalyzed, asymmetric method to directly functionalize pyridines, quinolines, and isoquinolines with terminal alkynes is described. The reaction is readily diversified to incorporate a range of pyridine-based heterocycles and electron-rich or electron-poor alkynes. This provides a straightforward alternative to nucleophilic or cross-coupling approaches to directly derivatize these heterocycles, and yields useful propargylcarbamates.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.