Studies on the Synthesis of (2<i>R</i>,4′<i>R</i>,8′<i>R</i>)‐α‐Tocopherol Alternative Syntheses of 2‐Chroman‐acetic Acid Intermediates

Abstract

Abstract As an extension of previous studies on the total synthesis of (2R,4′R,8′R)‐α‐tocopherol ( 1 ) [1] [2], (S)‐(−)‐2‐(6‐benzyloxy‐2,5,7,8‐tetramethylchroman)acetic acid ( 6 ), a pivotal intermediate, possessing the absolute configuration required for construction of 1 was prepared by optical resolution of the racemic modification 11 . the latter substance was obtained by two routes, one emanating from the hydroxy acetal 7 [1] and the other based upon the Lewis acid mediated cycloaddition of trimethylhydroquinone to rac.‐3‐hydroxy‐3‐methylpent‐4‐en‐l‐yl acetate ( 16 ) giving rac. ethyl 2‐(6‐hydroxy‐2,5,7,8‐tetramethyl‐chroman)acetate ( 12 ).