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The Adenosine A2A receptor is a member of the G-protein coupled receptor superfamily. It plays a key role in numerous physiological processes through the central nervous system and in peripheral tissues. Functional interactions between the A2A and dopamine D2 receptor has spurred interest in the use of antagonists as anti-Parkinson drugs. Additionally, oncology drugs are now being designed based on the potential for A2A antagonists to function as immunotherapeutics. From early studies based on classical xanthine type A2A antagonists through second generation agents, this mini review will cover aspects of the discovery, development, chemical synthesis and medicinal evaluation of this important class of drugs.

Positron emission tomography [PET] is a powerful nuclear clinical imaging technique used for the detection and treatment of central nervous system (CNS) disorders, cardiovascular diseases, and certain cancers. Due to the often short half-lives of the radiolabeled compounds employed, the availability of relevant tracers is severely limited. Through the use of microfluidic techniques many of the limitations of conventional synthesis of radiotracers are alleviated, paving the way for diverse families of compounds to be developed with defined targets for imaging. This review will survey syntheses of various radiotracers using new microfluidic techniques being developed.

Nuclear imaging using positron emission tomography [PET] is a powerful technique with clinical applications which include oncology, cardiovascular disease and CNS disorders. Conventional chemical syntheses of the short half-life radionuclides used in the process however imposes numerous limitations on scope of available ligands. By utilizing microwave assisted synthesis methods many of these limitations can be overcome, paving the way for the design of diverse families of agents with defined cellular targets. This review will survey recent developments in the field with emphasis on the period 2006-2011. Positron emission tomography [PET] has become one of the most powerful in vivo imaging modalities, capable of delivering mm3 resolution of radiotracer distribution and metabolism [1]. When combined with anatomic imaging methods (MRI, CT) co-registered multimode images offer the potential to track metabolic and physiologic events in diseased states and guide and accelerate clinical trials of investigational new drugs. Also, this same methodology can be used to evaluate first pass pharmacokinetics/pharmacodynamics in early stage drug discovery. Though powerful as a technique only a limited number of drugs have seen clinical use and to date only one drug 2-fluoro-deoxy-D-glucose (FDG) has received FDA approval [2]. One of the drawbacks of PET imaging is the need for tracers labeled with an appropriate nuclide and the half-lives of these agents places special constraints on the chemical synthesis. Among the most popular are 11C (t½ =20.4 min) and 18F (t ½ =109.8 min) labeled compounds and this has resulted in a resurgence of interest in practical application of their chemistries [3,4]. This review will focus on microwave mediated methods of acceleration of organic reactions used for the production of labeled PET image contrast agents, with emphasis on the five year period 2006 to 2011.

Positron emission tomography (PET) imaging of Alzheimer's Disease (AD) offers the potential to provide early onset diagnosis and subsequent intervention, including guided treatment regimens. One of the restricting factors in clinical application of PET technology is the limited availability of radioligands with affinity to specific targets of interest. Given the short half-life of the most popular positron emitter currently used ((18)F; approximately 120 min.) extremely rapid and efficient radiochemistry methods are needed to ensure required compounds are prepared and purified for administration within the 2-3 half life practical limit. Recent efforts to combine microwave mediated synthesis with advanced catalysis in the synthesis of specific categories of AD imaging agents will be presented.

Of the commonly recognized structural elements within nucleic acids, bulges are among the least developed as targets for small molecules. Bulges in DNA and RNA have been linked to biomolecular processes involved in numerous diseases, thus probes with affinity for these targets would be of considerable utility to chemical biologists and medicinal chemists. Despite such opportunity, there is a dearth of small molecules available with affinity for bulges, which has hampered exploitation of these key targets. We have used guided chemical synthesis to prepare small molecules capable of binding to DNA and RNA bulges. Our design is based on a template which mimics a metabolite of the enediyne neocarzinostatin. The key spirocylic building block was formed through an intramolecular aldol process and the parent template shows pronounced affinity for 2 base bulges. Functionalization with specific aminosugar moieties confers nanomolar binding affinity for selected bulged DNA targets, and installation of reactive functional groups allows covalent modification of bulges. These rationally designed agents can now be used to study the stereochemistry and architecture of bulge-drug complexes and investigate the molecular biology of bulge induced processes. Members of this class have been shown to induce slipped synthesis of DNA, suggesting the agents, in addition to recognizing and binding to pre-formed bulges, can also induce bulge formation on demand.

The enediynes remain among the most potent antitumoral agents to have been discovered in the past decade. Following prodrug activation, the enediynes undergo cycloaromatization reactions resulting in formation of highly reactive diradical intermediates. The diradical species engage in atom-transfer chemistry to produce neutral arene products, in the process inducing damage to key macromolecules. Several of the naturally occurring members of the enediyne family of antibiotics have entered clinical trials, and this has prompted the design of synthetic enediynes, where the enediyne lquo;warheadrquo; is conjugated to a targeted delivery vehicle. This review will describe ecent efforts using chemical synthesis to identify and improve the target specificity of designed enediynes, and to establish efficient methods to achieve prodrug activation. Finally, new horizons will be examined, including the use of post-cycloaromatized enediyne templates as recognition elements for unique DNA and RNA microenvironments.