THERMAL AND LEWIS ACID-PROMOTED NOVEL ASYMMETRIC HETERO-DIELS-ALDER REACTIONS OF A 1-THIABUTA-1,3-DIENE SYSTEM (THIOCHALCONES) WITH (-)-DIMENTHYL FUMARATE

Thermal and Lewis acid-promoted reactions of thiochalcones with (-)-dimenthyl fumarate gave two 3,4-cis-cycloadducts, 4 and 5, in good yields with 100% endo-diastereoselectivity and with a high level of diastereofacial selectivity. The major product 4 could be obtained stereochemically pure by recrystallization and this, when reduced with LiAIH4, gave the optically active diol 6. The latter was converted into the acyclic diol 8 by Raney-Ni desulphurization.