Discovery Of A New Mannich Reaction And Its Application In The Study Of HDAC Inhibitors

Mannich reaction is a famous three-component reaction,which is widely used in pharmaceutical chemistry,total synthesis of natural products,material science and other fields.The classic Mannich reaction is an alkylamination reaction between aldehydes,amines,and active carbon nucleophilic reagents(including aldehydes,ketones,indoles and other electron-rich aromatic rings),which can rapidly introduce structural diversity.However,Mannich reaction involving non-activated alkyl is still a great challenge.During the drug discovery research of Tanshinone IIA,I unexpectedly found a new Mannich reaction and realized the participation of inactive C(sp3)-H in Mannich reaction for the first time.On the basis of exploring and clarifying the reaction process,the double Mannich reaction involving electron-rich 3-methylbenzofuran analogues,aldehydes and amines was developed,and a novel benzofuran piperidine framework was constructed.Through further mechanism research,we propose a possible mechanism.Since benzofuran piperidine is the electronic isosteric of the dominant backbone of carbaline and other drugs,we applied this new Mannich reaction to drug research and development.Taking HDAC inhibitor as an example,we designed and synthesized the HDAC inhibitor with benzofuran piperidine parent nucleus.The selected compound has good HDAC inhibitory activity,and has shown good efficacy in vitro and in vivo evaluation of liver cancer,with good pharmacokinetic characteristics.In addition,this paper also developed the cyclization of a class of amide(or sulfonamide)with nitrous oxide under the condition of no additional oxidant,and constructed the 1,2,3-benzotriazine-4-one parent heterocyclic skeleton.Part I: Study on a new multi-component double Mannich reaction.With electronrich 3-alkyl benzofuran,formaldehyde and primary amine as substrates,we found that the reaction in acetic acid can synthesize benzofuran piperidine skeleton with high yield,and the reaction substrate has wide applicability.Through control experiment,deuterium labeling experiment and DFT calculation,the unique and novel reaction mechanism of the new double Mannich reaction was clarified,and the activation process of the inactive alkyl was revealed.This work provides new methods and possibilities for the expansion and application of Mannich reactionPart II: Design,synthesis and bioactivity evaluation of novel HDAC inhibitors.After developing a new multi-component Double-Mannich reaction,we have applied this reaction to the synthesis of small molecule drugs.Through scaffold-hopping design,we designed a series of HDAC inhibitors containing a new benzofuran-fused piperidine Cap structure,which could be rapidly synthesized by the novel Double-Mannich reaction.Among them,compound 3-19 k had robust HDAC1 inhibitory activity and can strongly inhibit the proliferation and migration of human hepatoma cell lines Bel7402,Hep G2 and Huh-7.In the mechanism study,3-19 k could effectively up-regulate the acetylation level of intracellular histone H3 and α-Tubulin of Tubulin,which would induce apoptosis and autophagy of HCC cells.In the xenograft model of liver cancer,the compound also showed better antitumor activity than sorafenib and SAHA,opening up a new direction for the research and development of liver cancer drugs.Part III: Study on the cyclization reaction of amide and sulfonamide with nitrous oxide.Under the reaction condition without any other oxidant,we successfully realized the cyclization reaction of benzamide and benzenesulfonamide with nitrous oxide to synthesize 1,2,3-benzotriazine-4-one scaffold.Among them,benzamide and benzenesulfonamide form lithium species through Do M process and react with nitrous oxide.This reaction provides a new method to synthesize 1,2,3-benzotriazine-4-one scaffold,which is simple in operation and wide in substrate universality.