Efficient and Green Synthesis of New Polycyclic Procyanidin Derivatives Via Tandem Dinucleophilic Addition of Indolin-2-Thiones to Flavylium Salts (Report‪)‬

INTRODUCTION Procyanidins are widespread in nature, and their applications to biologically active pharmaceuticals and functional materials are becoming more and more important [1]. A variety of molecules containing the procyanidins display a wide range of biological activity and find applications as anticancer, antiallergy, antioxidant, antibacterial, and hair-growing agents [2]. Besides, sulfurcontaining procyanidin skeletons are noticeable because they act as scavengers for preventing or treating lifestyle-related diseases like cancer, cardiovascular diseases, premature aging, and food supplement [3]. However, procyanidins are difficult to synthesize, and limited attention has been given to the synthesis of these compounds [4].