The regioselectivity of aziridine ring cleavage by nucleophiles (Cl−, Br−, I−, N3−, HBr) in a series of N-tosyl- and N-benzylepimino derivatives of 1,6-anhydro-β-D-hexopyranoses of D-allo, D-manno and D-galacto configurations has been studied. On treatment with halide anions, the tosylepimines 1, 3, 5 and 7 were opened trans-diaxially according to the Furst−Plattner rule. The courses of the reactions of benzylepimines 2, 4, 6 and 8 depended strongly on the configuration of the epimine and partially on the type of nucleophile used. On treatment with bromide and iodide, N-benzylepimines of D-allo (compounds 2, 4) and D-galacto (compound 6) configuration gave products of trans-diequatorial cleavage, while the manno-epimine 8 was opened trans-diaxially. In comparison, the reactions of all benzylepimines with azide and hydrobromic acid were independent of the configuration and proceeded trans-diaxially. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)