s = ChemicalData["Glucose", "MoleculePlot"];
Manipulate[
  If[r == 1, S = s[[1, 1]]];
  If[r == 2, S = s[[2, 1]]];
  If[r == 3, S = s[[3, 1]]];
  If[r == 4, S = s[[4, 1]]];
  Show[Graphics3D[S]], {{r, 1, "Molecules:"}, {1 -> "1", 2 -> "2", 3 -> "3", 4 -> "4"}}]