Herein, we report design, synthesis, and evaluation of a new Arginine-containing macrocyclic hydroxamate analog, RYM, its hydrazinonicotinamide conjugate, RYM1 and 99mTc-labeled analog 99mTc-RYM1 for molecular imaging. are in high demand. RP805, is a 99mTc-labeled macrocyclic hydroxamate MMP inhibitor (Fig.?1). Over the past decade, this tracer has been studied for MMP-targeted single-photon emission computed tomography (SPECT) imaging of cardiovascular and other pathologies in several preclinical models16C22. In vascular pathology, such as atherosclerosis and aneurysm, tissue uptake of RP805 correlates with vessel wall MMP activity and inflammation. Accordingly, this agent may be used to characterize atherosclerotic lesions, and evaluate aortic aneurysm progression and rupture risk. However, RP805 has a relatively prolonged blood circulation which may not be optimal for early time imaging of vascular diseases. In addition, the poor water solubility of RP805 precursor has impeded blocking studies at suitable concentrations. Lurasidone (SM13496) Therefore, we sought to pursue new macrocyclic hydroxamate analogs and related imaging agents with improved physicochemical properties for MMP-targeted imaging and therapy, with the ultimate goal of future clinical translation. Open in a separate window Figure 1 Structures of Lurasidone (SM13496) MMP-targeted SPECT imaging agent RP805 and its precursor. Previous studies performed on anti-succinate-based hydroxamic acids have elucidated the structural requirements of this class of inhibitors for anti-MMP activity, which include a hydroxamate as a zinc-binding site, as well as , P1, P2 and P3 substituents1. The preferred conformation of this type of inhibitors displays and P2 substituents on the same side with close proximity spatially, which can be cyclized as shown in RP805 and its precursor. Wide variations of P3 substituent can be tolerated. Based on this structure-activity relationship (Fig.?2), we designed a new macrocyclic hydroxamate-based analog, RYM, containing an Arginine (Arg) residue at P3 position for improving the hydrophilicity. Furthermore, we designed an analog, RYM1, containing a hydrazinonicotinamide (HYNIC) as a precursor for 99mTc-labeling to form 99mTc-RYM1 for pilot studies. Herein, we report the related synthesis, 99mTc labeling, MMP inhibition, and other evaluations and evaluation of 99mTc-RYM1, including biodistribution, imaging and binding specificity in murine models of carotid and aortic aneurysm, is reported elsewhere23. Open in a separate window Figure 2 Molecular design of novel arginine-containing hydroxamate-based MMP inhibitors. RYM, RYM1, and SPECT imaging agent 99mTc-RYM1. Results Synthesis As shown in Fig.?3, the synthetic strategy includes an initial synthesis of a protected anti-succinate-based macrocyclic acid analog (I-7)24,25. The synthesis was started from an anti-succinic acid derivative, i.e. (2R,3S)-3-(tert-butoxycarbonyl)-2-isobutylhex-5-enoic acid which was first converted into its benzyl ester (I-1) in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and benzyl bromide in toluene. Hydroboration of I-1 by 9-borabicyclo[3.3.1]nonane (9-BBN) in tetrahydrofuran (THF), followed by oxidation with H2O2, gave the hydroxyl derivative (I-2). The conversion of I-2 into its bromide derivative (I-3) was achieved using CBr4 and triphenylphosphine (Ph3P) in dichloromethane (DCM). Lurasidone (SM13496) The benzyl ester group of I-3 was removed by catalytic hydrogenation to give its acid analog (I-4). Coupling of I-4 with L-tyrosine benzyl ester in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDCI) and hydroxybenzotriazole (HOBT) in N,N-dimethylformamide (DMF) gave the anti-succinate-tyrosine benzyl ester (I-5). Cyclization of I-5 in the presence of Cs2CO3 in anhydrous acetonitrile gave the protected anti-succinate macrocyclic derivative (I-6). Finally, the macrocyclic acid analog (I-7) was obtained by detatching the benzyl band of I-6 in the current presence of 10% palladium on carbon (Pd/C) and HCOONH4 in methanol. Open up in another window Amount 3 Synthesis of the anti-succinate-based macrocyclic acidity intermediate (I-7). As depicted in Fig.?4, we used Fmoc-Arg(Mtr)-OH seeing that Rabbit Polyclonal to Paxillin (phospho-Ser178) the starting materials Lurasidone (SM13496) as the protecting group Mtr is steady in trifluoroacetic acidity (TFA) solution weighed against another widely used protecting group Pbf in Fmoc-Arg(Pbf)-OH26. As a result, Fmoc-Arg(Mtr)-OH was initially Lurasidone (SM13496) reacted with CH3NH2 in the current presence of EDCI/HOBT in DMF to provide Fmoc-Arg(Mtr)-NHCH3 (I-8). De-protection of I-8.