Toward the development of a general chiral auxiliary. Part 6: Structural effects on diastereoselection using camphor derived lactams: evaluation of (1R,4S)-1,7,7-trimethyl-3-azabicyclo[2.2.1]hept-5-en-3-one as a chiral controller

A new camphor-derived chiral lactam was designed, prepared and evaluated as a chiral controller in asymmetric Diels–Alder and aldol reactions. The new lactam, bearing a C(5)C(6) double bond, was anticipated to afford higher diastereofacial selection resulting from the removal of additional steric hindrance to reagent approach distal to the geminal dimethyl bridge by comparison with the previously studied saturated analogue (the favored mode approach in the saturated analogue). Surprisingly, a deterioration in the extent of diastereofacial selectivity was observed for both reaction types. These results are interpreted in terms of the geometric changes imposed upon the ring system as a whole by introduction of the unsaturation.