Cyclic guanidines. XVI. Synthesis and biological activities of tetracyclic imidazo[2,1-b]quinazolinone derivatives

An I2-mediated cascade reaction of 2'-bromoacetophenones with benzohydrazides/benzamides leading to quinazolino[3,2-b]cinnoline or tryptanthrin derivatives

An efficient and facile protocol for the synthesis of quinazolinone-fused tetracyclic compounds through an iodine-mediated one-pot cascade reaction of 2'-bromoacetophenones with 2-aminobenzohydrazides or 2-aminobenzamides is reported. With 2-aminobenzohydrazides as the substrates, the reaction gave 5H-quinazolino[3,2-b]cinnoline-7,13-diones in moderate to good yields under metal-catalyst-free conditions. With 2-aminobenzamides as the substrates and CuBr as the catalyst, on the other hand, it afforded tryptanthrin derivatives with good efficiency. Mechanistically, the formation of the tetracyclic systems is initiated by iodination and oxidation of 2'-bromoacetophenones followed by a cascade procedure consisting of cyclocondensation, aromatization and intramolecular cyclization of the in situ formed 2-bromoarylglyoxals with 2-aminobenzohydrazides or 2-aminobenzamides, respectively.

Nitrosative cytosine deamination. An exploration of the chemistry emanating from deamination with pyrimidine ring-opening

A discussion of nitrosative deamination of cytosine 1 is presented that argues for the formation of 6 by diazotization of 1 to cytosinediazonium ion 2 and its electrostatic complex 3, dediazoniation to 4 <--> 5, and amide-bond cleavage to 6. The reaction channels available to 6 include hydrolytic deglycation to 3-isocyanatoacrylonitrile 7, water addition to carbamic acid 9 with the possibility for re-closure to uracil 13, water addition to carbamic acid 9, and decarboxylation to 3-aminoacrylonitrile 10. With a view to the instability of the carbamic acid 9, the carbamate models ethyl (Z)-2-cyanovinylcarbamate 14 and (Z)-2-cyano-1-tert-butylvinylcarbamate 20 were studied. Acid-catalyzed hydrolysis of 14 leads to 2-amino-carbonylphenylcarbamate 15, and its cyclization yields the benzo-fused uracil quinazoline-2,4-dione 16. In contrast to the aromatic system 14, acid-catalyzed cyclization cannot compete with oligomerization in the case of 20, and 5-tert-butyluracil 22 is accessible only with base-catalysis. It is shown that 23, the parent of 10, also easily polymerizes. The experimental results provide a rationale as to why 9, 10, and 12 would have escaped detection in in vitro studies: they would have oligomerized. In contrast to the in vitro experiments, the oligomerizations of 9, 10, or 12 clearly are not relevant in vivo because of low monomer concentrations. With the exclusion of recyclization and of oligomerization in vivo, attention thus needs to focus on (Z)-3-aminoacrylonitrile 10 as the most likely deamination product of cytosine aside from uracil.

Determination of 7-piperidino-1,2,3,5-tetrahydroimidazo[2,1-b]quinazolin-2-one (DN-9693) in human plasma and urine by high-performance liquid chromatography with electrochemical detection: application to studies on disposition of DN-9693 in healthy human volunteers

A procedure for the determination of a newly developed antiadhesive agent, 7-piperidino-1,2,3,5-tetrahydroimidazo[2,1-b]quinazolin-2-on e (DN-9693; 1), in human plasma and urine at low nanogram levels by high-performance liquid chromatography with electrochemical detection is described. Plasma and urine samples were made alkaline with 1 M KOH solution and extracted with chloroform. After removing organic solvent, the extracts reconstituted in methanol were applied to a reversed-phase octadesyl-packed column and eluted with a methanol: phosphate buffer (pH 8.0) mobile phase. The applied potentials were set at 0.80 and 0.95 V versus a silver-silver chloride reference electrode for the analyses of plasma and urine specimens, respectively. The method provides a recovery of greater than 90% and a within-day precision of less than 5%. The minimum quantifiable levels for 1 in plasma and urine using 1 mL of sample are 1 and 4 ng/mL, respectively. The method has been successfully used for the determination of 1 in plasma and urine samples from healthy human volunteers after intravenous infusion of the drug.