Proximity-assisted cycloaddition reactions--facile Lewis acid-mediated synthesis of diversely functionalized bicyclic tetrazoles.

Aliphatic azidonitriles separated by three or four carbon atoms undergo facile Lewis acid-induced cycloadditions to give bicyclic tetrazoles, even at 0 degrees C. Extension to 3-azido-2-aryl-1,3-dioxolanes and the corresponding 1,3-dioxanes in the presence of TMSCN and BF3.OEt2 leads to a series of diversely functionalized novel oxabicyclic tetrazoles.

Total synthesis of N-malayamycin A and related bicyclic purine and pyrimidine nucleosides.

Methods are described for the total synthesis of bicyclic perhydrofuropyran nucleosides as N-analogues of the naturally occurring malayamycin A. Formation of the N-nucleosides relied on the activation of thioglycosides, proceeding via sulfonium intermediates. Ring closure metathesis was used in two approaches to build the bicyclic dioxa heterocycle.