cis-1-Ethyl-4,4,6,8-tetramethyl-2-tosyl-2,3,3a,4,6,7,8,9-octahydro-1H-pyrrolo[3′,4′:3,4]pyrano[6,5-d]pyrimidine-7,9-dione

In the title compound, C22H29N3O5S, the pyrrolidine ring is cis-fused to the dihydropyran ring. The pyrrolidine and dihydropyran rings adopt twist and half-chair conformations, respectively. The molecule is in a folded conformation; the sulfonyl-bound benzene ring lies over the pyrimidinedione ring, with a weak π–π interaction [centroid–centroid distance = 3.6147 (4) Å]. A weak intramolecular C—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, molecules are linked into a three-dimensional network by C—H⋯O hydrogen bonds.

In the title cis isomer, the pyrrolidine ring (N1/C1-C4) adopts a twist conformation compared to envelope conformations in the two independent molecules of the trans isomer. The trans -fusion results in an extended ring system, with the tosyl group bending away from the fused ring system. In the cis-isomer, the molecule is in a folded conformation, with the sulfonyl-bound benzene ring lying over the pyrimidinedione ring. As a result of the folded conformation, the benzene and pyrimidinedione rings of the cis isomer are placed one over the other with weak π-π interactions (centroid-centroid distance = 3.6147 (4) Å).
A weak intramolecular C4-H4···O5 hydrogen bond generates an S(6) ring motif. The molecules exist as a C-H···O hydrogen-bonded dimer, generating a ring of graph-set motif R 2 2 (20). The dimers are linked into a three-dimensional network by C-H···O hydrogen bonds (Fig. 3).

Experimental
To a solution of barbituric acid (1 mmol) in toluene (20 ml) the corresponding 2-(N-prenyl-N-tosylamino]acetaldehyde (1 mmol) and a catalytic amount of the base ethylenediamine-N,N'-diacetate (EDDA) were added and the reaction mixture was refluxed for 12 h. After completion of the reaction, the solvent was evaporated under reduced pressure and the crude product was chromatographed using a hexane-ethyl acetate (8:2 v/v) mixture to obtain the title compound. The compound was recrystallized from ethyl acetate solution by slow evaporation.
supplementary materials sup-2 Refinement All H atoms were positioned geometrically and allowed to ride on their parent atoms, with C-H = 0.93-0.98 Å. The U iso values were set equal to 1.5U eq of the carrier atom for methyl H atoms and 1.2U eq for the remaining H atoms. A rotating group model was used for the methyl groups.   cis-1- 4,6,3,3a,4,6,7,8,4':3,4] Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq S1 0.583987 ( supplementary materials sup-9