... Tetrahedron. Volume 69, Issue 5, 4 February 2013, Pages 1532–1538. ... R 1 =H/Me), (2) Claisen rearrangement with decalin, (3) O-alkylation or O-benzylation of skeleton 5 with alkyl or benzyl bromide, (4) Grignard addition with arylmagnesium bromide and (5) oxidation with ...