Diastereopure Preparation of α-Benzotriazolyl 1-Azacycloalka[2,1-b][1,3]-oxazines and their Application as Versatile Chiral Precursors - Xu, Xuenong; Lu, Jun; Li, Rui; Ge, Zongming; Dong, Yanmei; Hu, Yuefei (Synlett, 2004)