Two introductory organic chemistry laboratory experiments are described based on the Diels-Alder reaction of 2,3,4,5-tetraphenylcyclopentadienone, which is synthesized prior to or in a one-pot reaction, with styrene. Students are presented with three possible products, the "endo" and "exo" diastereomers and the decarbonylated product, for the beautiful crystalline compound isolated. Analysis by IR and [superscript 1]H NMR spectroscopy aid investigators in proposing an initial structure for the product, but the solved X-ray crystal structure provides unequivocal evidence of its stereochemistry. Both versions of the synthesis introduce two important and atom economical reactions, employ the Karplus relationship for [superscript 1]H NMR interpretation, and illustrate the power of X-ray crystallography for molecular structure determination.