Improvements in the Synthesis of a Key α-tocopherol, Intermediate[sbnd] (s)-(−)-3,4-Dihydro-6-Hydroxy-2,5,7,8-Tetramethyll-2H-1-Benzopyran-2-Acetic Acid

Abstract

The (S)-(−)-chroman-2-acetic acid 5 and its derivatives are plvotal intermediates in various total syntheses of natural (2R,4′FJ,E′FJ)- a- tocopherol (1) developed in our laboratories. 1–5 Certain of these convergent schemes,^1–3 involving coupling of C₁₅-chroman and C₁₄-side chain units possessing very high enantiomeric and diastereomeric purities, have also proven useful for construction of all 7 stereoisomers of natural a-tocopherol.⁶