Kilogram Synthesis of a Second-Generation LFA-1/ICAM Inhibitor

The process development and the kilogram-scale synthesis of BMS-688521 (1) are described. The synthesis features a highly efficient telescoped sequence which utilizes previously described spirocyclic hydantoin (4b) to produce the final intermediate via an SNAR reaction. A final deprotection step affords BMS-688521 (1) in high quality with an overall yield of 65% from the key intermediate, spirocyclic hydantoin (4b).