Efficient and diversity-oriented total synthesis of Riccardin C and application to develop novel macrolactam derivatives

Riccardin C (RC, 1) is a macrocyclic bis(bibenzyl) natural product exhibiting remarkable biological activity as a nuclear liver X receptors (LXRs) ligand and a lipid metabolism mediator. RC is expected to be a lead compound to develop drugs for atherosclerotic diseases, and therefore exploiting diversity-oriented synthesis of RC is a promising approach to drug discovery. In this paper, we report novel total synthesis of RC (7.4% overall yield in 16 steps) by using the intramolecular SNAr reaction as key cyclization reaction. This is the first example of efficient macrocyclization using 3-nitro-4-fluorostilbene as an electrophile. The methodology could be applied to synthesize novel lactam analogs of RC. The diversity-oriented synthesis of RC is versatile method for the synthesis of various types of bis(bibenzyl) natural products and their derivatization.