Diastereoselective synthesis of trans-fused tetrahydropyran derivatives of 5H-dibenzo[a,d]cycloheptene

Abstract The epoxides derived from 5 H -dibenzo[ a , d ]cycloheptene and its 2-fluoro derivative were converted into the trans -fused hydropyran-3-one compounds (4a R* ,13b S* )-(12-fluoro-)4,4a,9,13b-tetrahydrodibenzo[3,4:6,7]cyclohepta[1,2- b ]pyran-3(2 H )-one and the corresponding 3-amino derivative via two separate sequences. These involved opening of the epoxide by either a propargyl or allylmagnesium reagent followed by tungsten-mediated cyclisation of the alkynol or OsO 4 -catalysed transformation into the diol.