Pronounced Steric Hindrance for Nitrogen Inversion in 1,3,4-Oxadiazolidines Asymmetric Nitrogen, Part 83. This work was supported by the Russian Foundation for Basic Research (RFBR) (grant No. 97-03-33021) and DFG-RFBR (grant No. 98-03-04119). O.T. thanks the Fonds der Chemischen Industrie for a doctorate scholarship. Part 82: D. A. Lenev, K. A. Lyssenko, R. G. Kostyanovsky, Izv. Akad. Nauk. Ser. Khim. 2000, N7