Vicinal Dianion of Triethyl Ethanetricarboxylate: Syntheses of (±)-Lichesterinic Acid, (±)-Phaseolinic Acid, (±)-Nephromopsinic Acid, (±)-Rocellaric Acid, and (±)-Dihydroprotolichesterinic Acid

The vicinal dianion 2 derived from triethyl ethanetricarboxylate reacted regioselectively with aldehydes and ketones at C(β) to provide paraconic acid derivatives 5a–f in moderate to high yields as mixtures of diastereoisomers. The paraconic acid derivatives 5e and 5f were utilized as the starting materials for the syntheses of (±)-lichesterinic acid (12), (±)-phaseolinic acid (13), (±)-nephromopsinic acid (14), (±)-rocellaric acid (15), and (±)-dihydroprotolichesterinic acid (16).