Diketopiperazines have been utilized as chiral auxiliaries for asymetr
ic Diels-Alder reactions. Cyclo-S-phenylalanyl-R-proline (2) was found
to be the most promising of these auxiliaries and afforded Diels-Alde
r adducts in high chemical yield (78-95%), with endo selectivities gen
erally greater than 9:1. The diastereoselectivities observed were comp
arable to the best previously published values. (C) 1997 Elsevier Scie
nce Ltd.