Stereoselective synthesis of the cis-275B decahydroquinoline ring system

The Diels–Alder precursor was constructed from readily available d-glutamic acid utilizing a series of functional group transformations. The stereocenter of the amino acid provided the desired stereochemistry at C2 and diastereoselectively directed the intramolecular Diels–Alder cyclization. This simultaneously generated the three remaining stereocenters and yielded a bicyclic intermediate with all four stereocenters of the target decahydroquinoline 275B.