We have synthesized a series of 2-aminoethoxydiphenyl borate (2-APB, 2,2-diphenyl-1,3,2-oxazaborolidine) analogs and tested their ability to inhibit thrombin-induced Ca 2ϩ influx in human platelets. The analogs were either synthesized by adding various substituents to the oxazaborolidine ring (methyl, dimethyl, tert-butyl, phenyl, methyl phenyl, and pyridyl) or increasing the size of the oxazaborolidine ring to seven-and nine-membered rings. NMR analysis of the boron-containing analogs suggests that each of them exist as a ring structure through the formation of an N3 B coordinate bond (except for the hexyl analog). The possibility that these boron-containing compounds formed dimers was also considered. All compounds dose-dependently inhibited thrombin-induced Ca 2ϩ influx in human platelets, with the 2,2-diphenyl-1,3,2-oxazaborolidine-5-one derivative having the weakest activity at 100 M, whereas the (S)-4-benzyl and (R)-4-benzyl derivatives of 2-APB were approximately 10 times more potent than the parent 2-APB. Two nonboron analogs (3-methyl and 3-tert-butyl 2,2-diphenyl-1,3-oxazolidine) were synthesized; they had approximately the same activity as 2-APB, and this implies that the presence of boron was not necessary for inhibitory activity. All of the compounds tested were also able to inhibit thrombininduced calcium release. We concluded that extensive modifications of the oxazaborolidine ring in 2-APB can be made, and Ca 2ϩ -blocking activity was maintained.2-Aminoethoxydiphenyl borate (2-APB; systematic name: 2,2-diphenyl-1,3,2-oxazaborolidine, compound 1) was originally described as an inhibitor of inositol 1,4,5-trisphosphate receptors (IP 3 R) in a variety of cells (Maruyama et al., 1997) and has been extensively used as a probe for examining calcium influx processes. 2-APB was inappropriately used in several studies to imply that IP 3 Rs were involved in storeoperated Ca 2ϩ entry (SOCE) . For a review of our current understanding of the nature of SOCE and how the SOCE channels are regulated, see Parekh and Putney (2005). It has been suggested that SOCE is mediated by members of the transient receptor potential canonical (TRPC), family although this has not been accepted universally (Parekh and Putney, 2005).Upon further investigation, it became evident that 2-APB, along with inhibition of IP 3 Rs, was also inhibiting SOCE directly in several cell types (Bakowski et al., 2001;Broad et al., 2001;Diver et al., 2001;Dobrydneva et al., , 2002Gregory et al., 2001;Iwasaki et al., 2001;Ma et al., 2001;Prakriya and Lewis, 2001;Bootman et al., 2002). The inhibition of SOCE seemed to be at an extracellular site by a mechanism not involving intracellular IP 3 Rs. In our study showing that 2-APB blocked SOCE in human platelets (Dobrydneva and Blackmore, 2001), we tested whether several other structurally related compounds were also inhibitors of SOCE. We Some of the findings in this manuscript were presented at two meetings of the Virginia Academy of Science (Dovel et al., 2002;Thadigiri et al., 2003) and ...

Microfluidics technology has emerged as a powerful tool for the radiosynthesis of positron emission tomography (PET) and single-photon emission computed tomography radiolabeled compounds. In this work, we have exploited a continuous flow microfluidic system (Advion, Inc., USA) for the [(18) F]-fluorine radiolabeling of the malonic acid derivative, [(18) F] 2-(5-fluoro-pentyl)-2-methyl malonic acid ([(18) F]-FPMA), also known as [(18) F]-ML-10, a radiotracer proposed as a potential apoptosis PET imaging agent. The radiosynthesis was developed using a new tosylated precursor. Radiofluorination was initially optimized by manual synthesis and served as a basis to optimize reaction parameters for the microfluidic radiosynthesis. Under optimized conditions, radio-thin-layer chromatography analysis showed 79% [(18) F]-fluorine incorporation prior to hydrolysis and purification. Following hydrolysis, the [(18) F]-FPMA was purified by C18 Sep-Pak, and the final product was analyzed by radio-HPLC (high-performance liquid chromatography). This resulted in a decay-corrected 60% radiochemical yield and ≥98% radiochemical purity. Biodistribution data demonstrated rapid blood clearance with less than 2% of intact [(18) F]-FPMA radioactivity remaining in the circulation 60 min post-injection. Most organs showed low accumulation of the radiotracer, and radioactivity was predominately cleared through kidneys (95% in 1 h). Radio-HPLC analysis of plasma and urine samples showed a stable radiotracer at least up to 60 min post-injection.