Highly stereoselective construction of the C2 stereocentre of α-tocopherol (vitamin E) by asymmetric addition of Grignard reagents to ketones

摘要: Tertiary alcohol precursors of both C2 diastereoisomers α-tocopherol were prepared in three ways by our recently reported asymmetric Grignard synthesis. The versatility chemistry inherent its three-way disconnection was exploited to allow the synthesis product grades: 77 : 23 dr (5 steps), 81 : 19 steps) and 96 : 4 (7 steps, one gram scale) from readily available abundant starting materials. products converted their respective α-tocopherols 3 which allowed a definitive re-assignment absolute configurations.