... Chemical shifts for other signals are all in accordance with the structure proposed. ... [la] R. Stolle, J. Prakt ... Rev., 10, 508 (1964); [d] A. Hetzheim and K. Mockel, Advances in Heterocyclic Chemistry, Vol 5, Academic Press, New York, 1966, p 183; [e] FN Hayes, BS Rogers and DG Ott ...