The synthesis and in vitro anti-tumor 60 cell lines screen of a novel series of anthracenyl isoxazole amides (AIMs)¥ (22-33) is described. The molecules consist of an isoxazole that pre-organizes a planar aromatic moiety and a simple amide and/or lexitropsin-oligopeptide. The new conjugate molecules were prepared via doubly activated amidation modification of Weinreb's amide formation technique, using SmCl 3 as an activating agent which produces improved yields for sterically hindered 3-aryl-4-isoxazolecarboxylic esters. The results of the National Cancer Institute's (NCI) 60 cell line screening assay show a distinct structure activity relationship (SAR), wherein a trend of the highest activity for molecules with one N-methylpyrrole peptide. Evidence consistent with a mechanism of action via the interaction of these compounds with G-quadruplex (G4) DNA, and a structural based rational for the observed selectivity of the AIMs for G4 over B-DNA is presented.

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A critical comparison of methods to prepare sterically hindered 3-aryl isoxazoles containing fused aromatic rings using the nitrile oxide cycloaddition (NOC) reveal that modification of the method of Bode, Hachisu, Matsuura, and Suzuki (BHMS), utilizing either triethylamine as base or sodium enolates of the diketone, ketoester, and ketoamide dipolarophiles, respectively, was the method of choice for this transformation.

Dimeric analogs of Anthracenyl Isoxazole Amides (AIMs) (the designation AIM is in honor of the memory of Professor Albert I. Meyers) were prepared and dimer 6 exhibited the highest efficacy to date for this class of anti-tumor compounds against the human glioma Central Nervous System cell line SNB-19.We recently reported the anti-cancer activity of a new series of Anthracenyl Isoxazole Amides (AIMs), 1 which exhibited significant activity in the 60 Cell Line protocol at the National Cancer Institute (NCI60). 2 Our working hypothesis is that this novel class of compounds exert their effect by stabilization of quadruplex (G4) DNA, 3 either at the telomere 4 and/or specific oncogenes. 5 Recently it has been postulated that the telomeric overhang of the human chromosomes possibly form multiple G4 conformers, 4a,b if this argument is correct, one classic 6 test of this hypothesis would involve the tethering of G4 binding moieties, with the expectation of enhanced biological effect.Two methods were compared for the preparation of the AIM dimers 4-6. Method A utilized our previously reported lanthanide assisted Weinreb amidation, 7 or double activation methodology. 1b Method B is a straightforward Schotten-Baumann process.The advantage of the double activation method is its directness, and it generally proceeds in overall synthetically useful yields after isolation and purification, however, in the case of AIM 4 a 2 to 1 ratio of dimer to mono-AIM incorporation was observed, though the material balance was near quantitative after the recovery of starting material. The double activation procedure was originally developed for amide couplings which were both sterically hindered and either Correspondence to: Nicholas R. Natale. Supplementary Material: Full experimental details for preparation of synthetic dimers 4-6, procedure for Cell Culture and Growth Inhibition Assays. NSC numbers and one-dose data of for 5 and 6 and five-dose data for 6, in the NCI60 protocol. Calculated logD graph for 6. HSQC 2D NMR of dimer 5. Pharmacokinetic computations for AIMs 4-7.Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. contained functional groups incompatible with thionyl or phosphorus halides (i.e. acridines) or could be potentially chlorinated (i.e., C-10 H anthryl). 1b,9 Our recent observation that the C-10 chloro derivative 7 actually possessed higher anticancer activity1a lead us to reexamine the more conventional Schotten-Baumann route. The three step Schotten-Baumann procedure first necessitates a hydrolysis, which due to the steric hindrance of the anthryl moiety proceeded in a v...