A short synthesis of the carbocyclic core of Entecavir from Corey lactone

The readily available Corey lactone was converted in three simple stages to tris-TBS-ether of (1R*,3R*,5S*)-1-hydroxymethyl-3,5-dihydroxy-2-methylidenecyclopentane – the protected carbocyclic core of Entecavir, one of the best medicines against hepatitis.