Imidazo piperazines

Chemical Name 8-Nitro-1,2-dihydro-2-(N-methyl-piperazin-1 -yl)methylene-6-(o-chloro-phenyl)-1 H,4H-imidazo-[ 1,2-a] [ 1,4] -benzodiazepin-1 -one methanesulfonate... 

Some very clever syntheses of pyrazines were reported. Tandem Mn02-mediated oxidation followed by in situ trapping with aromatic or aliphatic 1,2-diamines was shown to give rise to quinoxalines, dihydropyrazines, pyrazines, and piperazines without the need to isolate highly reactive 1,2-dicarbonyl intermediates <03CC2286>. A new intramolecular cyclization route to highly substituted chiral 6,7-dihydro-5//-imidazo[l,5-a]pyrazin-8-ones like 157 from Meldrum s acid was developed <030L3907>, and 5-chloropyrido[3,4-6]pyrazines were prepared from 1,2-dicarbonyl compounds and 2-chloro-3,4-diaminopyridine <03H(60)925>. A synthesis of... 

Studies on the tri-, tetra- and penta-peptides of a-methylalanine (65T3209, 73ACS1509) have shown that cyclization to the imidazo[l,2-a]pyrazine ring system occurs and a sequence for its formation from the tripeptide suggested (467) -> (468) -> (469). Another tripeptide cyclizes to a piperazine and then to the bicyclic system (78TL1009). 

This ring system has also been called l,3a,6-triazaindene and numbered as in formula 1. A third alternative numbering system (2) has also been used on one occasion. Partly reduced derivatives of imidazo[l,2-a]pyrazine have been referred to as imidazo[l,2-a]piperazines and others, as imidazolino[l,2-a]pyrazines. The majority of papers on this heterocycle are of recent origin and concern the structure and oxidation products of Cypridina luciferin, a bioluminescent substance isolated from Cypridina hilgendorfii, a small crustacean. 

SRT-1720 A typical representative of fully synthetic SIRTl activators is SRT-1720 (Fig. 4.20,8), which yields a protonated molecule using positive ESI that efficiently dissociates upon CID (Fig. 4.22b). Various ionization sites are provided including the quinoxaline, imidazo[2,l-b]thiazole, and the piperazine moieties, which complicated... 

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