AbstractA new series of conformationally locked N,O‐nucleoside analogues was synthesized by exploiting allenic nucleobases as dipolarophiles in 1,3‐dipolar nitrone cycloadditions. The regio‐ and sitoselectivity of the reaction were rationalized according to the frontier orbital treatment of the nitrone cycloaddition by AM1 calculations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)