Moreover, the computational studies using MOE 2014.09 software are confirming the results in biological activity.R23/24/25, R40, R41, R43, R48/23/24/25, R68, R50 Results: The results revealed that compounds 18 and 24 have good activities compared with Cefepime reference drug. Method: The newly synthesized products were evaluated for their antimicrobial activities. The structures of the newly synthesized compounds were confirmed by spectral data and elemental analyses. Pyridine analogs substituted in the 4-position with a pyridinones 18, 20, 22 or naphthofuran 24 were also synthesized. The reaction of 9 with hydrazonoyl chlorides 3 yielded products 13a-h. The enaminone 2 reacts also with 6-aminothiouracil (8) to yielded thione 9. Hydrazinolysis of 6a-c,e-f yielded the respective pyrazolopyridazines 7a-f. Ultimate, thermal decarboxylation with concomitant O-methyl deprotection and further N-benzyl deprotection by the action of triflic acid completed the synthesis of the target natural product variolin B.īackground: An efficient synthesis of hitherto unreported 4-heteroarylpyridines was described via regioselective 1,3-dipolar cycloaddition reactions of 3-(dimethylamino)-1-(pyridin-4-yl)prop-2-en-1-one (2) with nitrilimines 4a-h to afford the corresponding pyrazole derivatives 6a-h. Installation of the northeast 2-aminopyrimidine ring at C5 is performed using the Bredereck protocol (three steps).
Formation of the annelated pyrimidine ring is achieved by two routes both involving a carbodiimide-mediated cyclization process, which allow incorporation of the amine functionality at C9 of the core tricyclic (six steps). The required 7-azaindole ring appropriately substituted is formed by a modified indole synthesis involving a nitrene insertion process (two steps). Our approach is based on the sequential formation of the 7-azaindole ring, the tricyclic pyridopyrrolopyrimidine ring system, and finally installation of the 2-aminopyrimidine ring at C5. A total synthesis of the marine alkaloid variolin B has been completed in 13 steps in an overall yield of 6.5% from 3-formyl-4-methoxypyridine.
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