Bicyclic imides of the type illustrated in general structure 1 are of interest because they belong to a class of anti-Bredt bridgehead nitrogen amides.1 These compounds were first proposed as potential stereoselective anticonvulsants by E. E. Smissman, whose synthetic efforts2-11 revealed that structures with n = 1 were very resistant to formation. For example, despite numerous attempts by Smissman to prepare 1a (n = 1) or analogues, 6-8 the only reported success6 was for the preparation of methoxy-substituted bicyclic barbiturate 4 using the procedure illustrated in Scheme I. Surprisingly, similar synthetic approaches involving intermediates without the methoxy group, such as 5 in Scheme I, did not yield la. Our interest2 in these systems prompted us to repeat Smissman's synthesis of 4. Here we report that the structural assignments for 4 and the immediate synthetic precursor 3 are incorrect, and we provide NMR evidence which shows that the correct structures are novel cyclized barbituric acid derivatives containing the amide acetal functionality. © 1984, American Chemical Society. All rights reserved.