Bis-anthracenyl isoxazolyl amides have enhanced anticancer activity

Abstract

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...

AIMing towards improved antitumor efficacy

“…26 IC 50 values were determined from semi-log plots of percent of control versus concentration. Consistent with previous observations, 6,11 the use of SNB-19 cells as a prescreen was a good indicator of antitumor activity in the NCI 60. Compound 3c represents the most active antitumor compound in this series to date, and it is the first of the series with a submicromolar IC 50 (Table 1).…”

“…11 The acyl chlorides were then condensed with the bis-dimethylamino propyl pyrrole amine 6,11,12 under modified Schotten-Baumann conditions (Scheme 1 and Supplementary Data). Purification was accomplished via preparative TLC on silica gel eluting with 10% ammonium hydroxide in methanol.…”

Improved synthesis of 3-aryl isoxazoles containing fused aromatic rings

“…All compounds that were evaluated in biochemical and biophysical assays had >95% purity as determined by 1 H NMR and LCMS NSC 728558 was prepared from 3k as previously described. 8,9 …”

“…22 The ketamide was prepared from diketene and pyrrolidine, 18 and cycloaddition provided the C-4 amide in synthetically reasonable yield. The sluggish reactivity we previously reported for nucleophilic addition to the C-4 ester of the 3-anthryl-isoxazole is exemplified by (1) slow hydrolysis rates (i.e., 60 h using refluxing aqueous LiOH) 9 and (2) the observation that n -BuLi deprotonates the C-5 methyl at −78 °C without noticeable addition to the C-4 ester. 19 The C-4 functionalization prior to the NOC stage is a definite advantage for the preparation of AIMs, and will be the subject of further study.…”

“…1–4 The synthesis of aryl-isoxazoles is also the subject of on-going improvements. 1,5–7 In connection with our studies on aryl isoxazole amides (AIMs) 8–9 we have reported lead compounds, which possess (1) useful antitumor activity and (2) photophysical properties, which are of potential diagnostic use as ‘tumor paint’. 10 …”