Heterocyclizations in the pyrido[2,3-b]pyrazine series

Copper(II)-catalyzed indolizines formation followed by dehydrogenative functionalization cascade to synthesize 1-bromoindolizines

A one-pot, three-component cascade reaction between pyridine, α-acylmethylbromide, and maleic anhydride leading to direct access of 1-bromoindolizines in high yields has been developed. This protocol is accomplished via a reaction sequence of 1,3-dipolar cycloaddition of the pyridinium ylide with maleic anhydride, oxidative decarboxylation of the primary cycloadduct, and dehydrogenative bromination of the resulting 1-unsubstituted indolizine. Copper chloride was used as a catalyst and oxygen as the terminal oxidant. This reaction represents the first example of transition-metal-catalyzed direct dehydrogenative bromination of indolizine at the C-1 position. Moreover, the obtained 1-bromoindolizines can be transformed to other 1-substituted indolizines such as 1-arylindolizines via a simple reaction process.

Application of a 6pi-1-azatriene electrocyclization strategy to the total synthesis of the marine sponge metabolite ageladine A and biological evaluation of synthetic analogues

A 12-step synthesis of the angiogenesis inhibitory marine metabolite ageladine A is reported. The key steps include a 6pi-1-azatriene electrocyclization for formation of the pyridine ring and a Suzuki-Miyaura coupling of N-Boc-pyrrole-2-boronic acid with a chloroimidazopyridine. In addition, an assessment of the biological activity of a variety of synthetic analogues of ageladine A prepared during this synthesis is described.

Synthesis and evaluation of 6-methylene-bridged uracil derivatives. Part 1: Discovery of novel orally active inhibitors of human thymidine phosphorylase

A series of novel 6-methylene-bridged uracil derivatives have been prepared as inhibitors of human thymidine phosphorylase (TP). To enhance the in vivo antitumor activity of fluorinated pyrimidine 2'-deoxyribonucleosides such as 2'-deoxy-5-(trifluoromethyl)uridine (F(3)dThd), a potent TP inhibitor preventing their degradation to an inactive compound, has become a target of medicinal chemistry. We present here the synthesis and evaluation of novel human TP inhibitors. Introduction of an N-substituted aminomethyl side chain at the 6-position of 5-chlorouracil has improved water solubility and enhanced inhibitory activity compared with the known TP inhibitor, 6-amino-5-chlorouracil. Compound 42 was reasonably well absorbed in mice after oral administration. When combined with F(3)dThd, compound 42 exerted its TP inhibitory potency by increasing the maximum plasma concentrations of the former as evidenced in experiments with monkeys. Positive changes in pharmacokinetic profile were accompanied by the enhanced in vivo antitumor activity of this combination when compared to F(3)dThd alone, in mice bearing human tumor xenografts. Both biochemical and pharmacological effects appeared to fit the concept as anticipated.

Synthesis and in vitro cytotoxic evaluation of new derivatives of pyrido[1,2-a]benzimidazolic ring system: the pyrido[1',2':1,2]imidazo[4,5-h]quinazolines

Access to the original series of pyrido[1',2':1,2]imidazo[4,5-h]quinazoline was developed from a 1,3-dicarbonyl unit with some "N-C-N" bisnucleophilic reagents and the derivatives obtained were evaluated for in vitro cytotoxic activities against HL60 and A2780 cells. All compounds exhibited cytotoxic activities on resistant cell lines (MDR+; HL60R and A2780R) with no resistance phenomena.