Transamidation intramolecular, ring

Three independent syntheses of alkaloids of the celacinnine group have been published. In the synthesis of celacinnine (117) by Wasserman et al. (104), the central reaction used is the transamidation or Zip-reaction (69,105,106). In the first part, the preparation of the nine-membered intermediate 122 was achieved by two different routes. Heating of 4-phenylazeti-dinone (123) with 2-methoxypyrroline (124) led to the bicyclic 4-oxotetra-hydropyrimidine (125). The reaction seems to proceed via the tricyclic intermediate 126 and involves an intramolecular ring opening of a /J-lactam... 

The intramolecular transamidation of nine-membered rings has been exploited in the synthesis of macrocycles. Lactam (124), when treated with acid catalyst in refluxing xylene, gave the 13-membered ring (125) (Equation (6)) <92T3775> (see also <80TL3493 . 

---