A nucleophilic addition ring closure [NARC]-based synthesis of (+) -nonactic acid

Abstract

Nonactic acid 1 has been synthesized in 12 steps from readily available (S)-(−)-ethyl lactate in 20% overall yield. The key (“NARC”) sequence in this method involved anti-aldol addition of acylsultam 3 with aldehyde 4 followed by intramolecular oxymercuration. The efficiency and selectivity of the anti-aldol reaction was found to be critically dependent upon the ratio of Lewis acid to base. The intramolecular oxymercuration was also found to be highly diastereoselective and was attributed to allylic control consistent with previous studies in our group.