(2S,3R,4S,5R)-Diethyl 2-(10,10-dimethyl-3,3-dioxo-3lambda(6)-thia-4-azatricyclo[5.2.1.0(1,5)]decan-4-ylcarbonyl)-5-phenylpyrrolidine-3,4-dicarboxylate: a novel isomorphous-by-addition compound.

The title compound, C(27)H(36)N(2)O(7)S, (I), is isomorphous by addition with the dimethyl ester analogue [Garner, Dogan, Youngs, Kennedy, Protasiewicz & Zaniewski (2001). Tetrahedron, 57, 71-85], (II), by replacing two methyl ester H atoms with two methyl groups. With the exception of the conformation of one of the ester groups, the molecules are almost superimposable. Likewise, apart from a slightly larger c axis in (I), few differences in the cell packing of (I) and (II) are found, with both dominated by the same C-H...O hydrogen bonds. Full synthetic and spectroscopic details of (I) are given. The molecular synthesis is important as an example of chiral auxiliary-assisted 1,3-dipolar cycloaddition of an azomethine ylid.