M. Jayaraman et al., MODULATING STERIC EFFECTS IN DIASTEREOSELECTIVE STAUDINGER REACTION -SYNTHESIS OF OPTICALLY PURE CIS-BETA-LACTAMS, Tetrahedron, 52(10), 1996, pp. 3741-3756
Diastereoselection in the synthesis of beta-lactams (14 and 15) via ke
tene-imine cycloaddition (Staudinger reaction) using different chiral
auxiliaries has been examined. While sterically demanding imines deriv
ed from bicyclic aldehyde (1) with a beta chiral centre provided excel
lent selectivity, use of imines derived from bicyclic aldehyde (17) wi
th a gamma chiral centre was not effective. Improvement of stereoselec
tivity was also sought using imines (6 and 7) derived from chiral amin
es (2d,e) and chiral aldehyde (1). The bicyclic terpenoid skeleton of
the chiral auxiliary in 1 was dismantled by ruthenium tetroxide oxidat
ion to give multiply functionalized beta-lactams 23a-d in good yield.