Abstract Chiral acylnitroso dienophiles 14, which were obtained from L-proline and from D- mandelic acid, reacted with cyclohexa-1, 3-diene to give the expected diastereoisomers 15 and 16 (Scheme 2 and Table 1). The de values for these Diels-Alder reactions were moderate; they are related to the molecular stiffness of the dienophiles. The absolute configuration of the major cycloadducts was interpreted in terms of HOMO/LUMO ...
