Stereoselective Domino Semipinacol‐Schmidt Reaction: Diastereoselective Synthesis of 7 a‐epi‐(+)‐Lepadiformine C and Formal Synthesis of 7 a‐epi‐(−)‐Lepadiformine A

Abstract A concise approach has been developed for the diastereoselective synthesis of the azatricyclic core of (−)‐7 a‐ epi ‐lepadiformine A ( 8 a ) and (−)‐7 a‐ epi ‐lepadiformine C ( 8 b ) using stereoselective domino semipinacol‐Schmidt reaction as a key step. In presence of TiCl 4 , the oxaspiropentane‐azide derivatives underwent stereoselective domino cyclization to furnish the corresponding angularly fused azatricyclic cores in very good yields. Moreover, azatricyclic core of (−)‐7 a‐ epi ‐lepadiformine A has also been realized, in a stepwise manner, through the intramolecular Schmidt reaction of azido‐spirocyclobutanone intermediate. The synthetic utility of domino semipinacol‐Schmidt reaction is further shown in the diastereoselective synthesis of (+)‐7 a‐ epi ‐lepadiformine C ( 7 ).