Azacycloundecene ring

The fourth approach to the synthesis of manzamine C involved a Ramberg-Backlund rearrangement in the key step for the preparation of the azacycloundecene ring [81[. Synthesis ofthis ring began with thecondensationof5-amino-l-pentanol 156... 

The Ramberg-Backlund rearrangement was the key step in the total synthesis of the marine alkaloid manzamine C by D.l. MaGee and E.J. Beck. The azacycloundecene ring was stereoselectively formed by exposing the a-chloro sulfone to a strong base. The use of weaker bases either resulted in no reaction or gave rise to mixtures of ( )- and (Z)-alkenes. 

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