Tandem Semipinacol/Schmidt Reaction Leading to a Versatile and Efficient Approach to Azaquaternary Alkaloid Skeletons

A TiCl4-promoted tandem semipinacol/Aubé's type intramolecular Schmidt reaction of α-siloxy-epoxy-azide has been designed and developed
to be a general method for efficient construction of azaquaternary carbon units. As applicable examples, some key tricyclic azaquaternary
skeletons incorporated in many important alkaloids, such as cephalotaxine, stemonamine, erythrinan, and homoerythrinan alkaloids, have
been constructed.