e.g. Filippa Pettersson or Cancer Res. 75(6) , 1102-12, (2015) or 10.1002/anie.201600521
Synthesis of d-biotin from L-cystine via intramolecular [3+ 2] cycloaddition
…, HL Lee, G Pizzolato, MR Uskokovic
Index: Baggiolini, Enrico G.; Lee, Hsi Lin; Pizzolato, Giacomo; Uskokovic, Milan R. Journal of the American Chemical Society, 1982 , vol. 104, # 23 p. 6460 - 6462
In summary the zinc chloride-THF catalyst system would appear to have exhibited all of the characteristics to be expected of the pericyclic (type a) model. The required intermediate type, 3, is produced in a stereospecific reaction. No acyclic intermediates are observed. Strict suprafaciality, in addition to the diene, is apparently followed. The selective endo orientation of the diene has been rationalized? Finally, the trans&-diene 11 reacts much ...