For those of you with the BR organic chemistry books (Ch.4, #60): I was wondering why there were 8 instead of 4 total products from this asymmetric Diels Alder reaction. The answer key claims there are two possible structural isomers, each with two chiral centers. Therefore 4 stereoisomers for each structural isomer, for a total of 8 products. However, the Diels Alder reaction is stereospecific with syn addition, so it seems to me there would only be two stereoisomers for each structural isomer, for a total of 4 unique products. Shouldn't each structural isomer just consist of a pair of enantiomers?