Piperazines bicyclic, condensed

Compared with monocyclic piperazine scaffolds, bicyclic piperazines often provide platforms with even more points of diversity compared to monocyclic piperazines. Condensed bicyclic piperazines enlarge the chemical space of piperazine scaffolds, as well as the family of target proteins. For example, bicyclic piperazinones were prepared and evaluated in vitro and in vivo as thrombin inhibitors [49]. The cocrystal structure of a bicyclic piperazinone inhibitor 154 with thrombin was shown in Fig. 9. So far, chemists have developed many MCR methods to synthesize a variety of bicyclic piperazine scaffolds. 

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