Wednesday, October 21, 2009

Japp-Klingemann reaction and lots of anti-s

A 'just accepted' article in Bioorganic and Medicinal Chemistry (doi:10.1016/j.bmc.2009.10.012) caught my attention because of the number of "anti" activities stated in the title for a particlar 'new' class of compounds, 2-arylazobenzosuberones: "Synthesis, Tautomerism, Antimicrobial, Anti-HCV, Anti-SSPE, Antioxidant and Antitumor activities of Arylazobenzosuberones."  From one common precursor, 12 compounds were synthesized with variation of the arene group of the diazonium salt coupling power.  Reaction of 1-benzosuberone-2-dimethylaminomethylene with aryl diazonium chloride resulted in the Japp-Klingemann type cleavage of the dimethylaminomethylene group.

The Japp-Klingemann reaction normally involves the reaction of beta-keto esters or acids with aryldiazonium salts in the presence of base to form hydrazones, usually in aqueous medium but in alcohols if solubility is poor:


In this paper, however, an alpha-dimethylaminomethylene group functions as the original ketone in this case, so there's no need for a strong base - the conditions for the reaction are sodium acetate in ethanol at 0-5 °C for 20 minutes, then overnight in a refrigerator to crash out the product.



So for all the anti's - 8 of these compounds were tested for inhibitation of growth of 4 strains of bacteria and 4 strains of fungi using the agar diffusion method.  Referenced antibacterial drugs are mentioned, but not identified nor is comparison data for the standard included in the data presented in the form of Minimum Inhibitory Concentration (MIC) values.  The paper claimed much better activity of some of the compounds than the standards, but the units of the values are GRAMS per mL. That's HUGE to me... the lowest measured was 0.313 g/mL.  The tetra- and pentacyclic compounds below weren't tested, but I would've liked to see them tested, since the heteroarene rings are such great pharmacaphores and they're much different than the rest of the bicyclic azoketosuberones.



Antioxidant activity was assessed with the DPPH radical scavanging test, a colorimetric assay that determines XXX, with ascorbic acid (vitamin C) as a standard.  The second test was inhibition of ONOO- (ooohhhhnooooooooooooooooooo!) which can cause tissue damage from oxidation and nitration of lipids, proteins DNA and carbohydrates.  These results were in IC50 values, thank goodness, but like all the other biological activity tests, the hydrazones were just as good if only slightly better than the standards, if standard data was even shown.  They aren't orders of magnitude different.  What did I expect?

When I read these kinds of med chem type papers I take an especially harsh eye to it, definitely not because I'm a scientist and thus am cynical (which I definitely am), but because it's a habit from being a reviewer for a school journal.  Everything we got in seemed to me so unimpressive that I finally got fed up and quit being on the board.  The biological studies in this paper made me feel like that.  Please, please don't talk up your results.  Just tell them how they are and let the community decide whether or not your compounds are the shit.  When I just now got around to opening the Kürti and Czakó text, I wasn't surprised to see a similar ring system used to make a remarkably similar product by G. Primofiore and co-workers in 1993 (see below, from p.225)... ripoffs! Can't believe I wasted that time. The only thing I liked was that all the compounds were in the yellow/orange range in moderate to good yields... slightly redeeming.

Look familiar? 





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