Propionaldehyde, from degradation

C (and 7) was deduced by the formation of the heterosteroid F (or its equivalent from 7) by reaction with ammonia. The processes which lead from C to D and from 7 to 8 have been rationalized by Sih in identical chemical terms. Compound E is presumed to arise from D by further degradation. Sih and Wang and their collaborators also showed that 8 is further fragmented into 9 and thence to propionaldehyde and pyruvic acid. 

---