2020 Volume 78 Issue 4 Pages 304-316
In the course of our studies on the total synthesis of natural products, serious problems frequently arose due to the particular reactivity of synthetic intermediates. However, we attempted to exploit such potential reactivities, for developing new synthetic methods to achieve the total synthesis. An example in this context is the total synthesis of (−)-spiroxin C that was achieved by using a stereospecific photoredox reaction of naphthoquinone, which had been discovered during our synthetic effort toward bis-C-glycoside natural products. Dibenzobicyclo [3.2.1] octadienone structure is often embedded in the dimeric polyketide natural products. Although the intriguing motif has fascinated the synthetic community, no synthetic access had been established. By using bisnaphthoquinone acetal as the precursor to the bicyclic motif, we developed a reductive cyclization, in which thiolate worked as both a nucleophile and a reductant. Use of the asymmetric 1,4-addition of aryl pinacol borane and the reductive cyclization enabled the first total synthesis of (+)-engelharquinone and its epoxide.
