On the rapid synthesis of highly substituted proline analogues by 5-endo-trig iodocyclisation

Highly substituted α-alkenyl-α-amino esters undergo smooth if rather slow 5-endo-iodocyclisations both in the presence or absence of base to give good to excellent yields of substituted proline derivatives. The stereoselectivities are often only moderate, except when the amino ester residue carries a substituent, which is branched at its α-position.

Iodocyclisations of highly substituted α-sulfonylamino esters give excellent yields of proline analogues, with fair to good levels of stereocontrol.