Synthesis of chiral hexacyclic steroids via [8π + 2π] cycloaddition of diazafulvenium methides. - Lopes SM; Correia CF; Nunes SC; Pereira NA; Ferreira AR; Sousa EP; Gomes CS; Salvador JA; Pais AA; Pinho e Melo TM (Organic & biomolecular chemistry, 2015)