Synthesis of Spiro-Type Polyheterocyclic Compounds

Spirocycles have received considerable interest in the last decade as a privileged structural motif. The conformational restriction associated with the structural rigidity and the chirality of their quaternary center influences considerably their biological activities (antimicrobial, antitumor, antibiotic) 

SCHEME 6.28 Asymmetric inverse electron demand aza-Diels-Alder (lEDDA) reaction to yield fused heterocycles 200. 

SCHEME 6.29 Phosphoric acid-catalyzed Povarov reaction. 

SCHEME 6.30 Synthesis of multifunctionalized tetracyclic indeno[l,2-fc]indole derivatives 207 and 209. 

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