Efficient synthesis of tetrazole derivatives of cytisine using the azido-Ugi reaction

The azido-Ugi reaction with natural alkaloid cytisine was investigated. It was demonstrated that the reaction could be performed with various carbonyls (both aldehydes and ketones) and isocyanides. The transformation proceeded under mild conditions in methanol using TMSN3 as a source of hydrazoic acid to give target tetrazole derivatives of cytisine in up to 98% yield. The diastereoselectivity of this reaction was studied using both aliphatic and aromatic aldehydes. A family of tetrazole derived cytisine compounds was prepared. Selective deprotection of tetrazoles was elaborated to synthesize the corresponding NH-tetrazoles. © 2018