合成路线1

The esterification of (rac)-6-hydroxy-2,5,7,8-tetramethyl-3,4-dihydro-2H-1-benzopyran-2-carboxylic acid (XXII) with diazomethane gives the methyl ester (XXIII), which is treated with Bn-Br and K2CO3 yielding the benzyl ether (XXIV). The reduction of the ester group of (XXIV) with LiAlH4 provides the carbinol (XXV), which is debenzylated with H2 over Pd/C to afford the racemic phenol (rac)-(XXVI). Optical resolution of (XXVI) by means of lipase PL-266 and vinyl acetate gives the chiral acetate (S)-(XXVII), which is rebenzylated with BnBr yielding the benzyl ether (XXVIII). The deacetylation of (XXVIII) with LiAlH4 in ethyl ether affords the carbinol (XXIX), which is oxidized with oxalyl chloride to the aldehyde (XXX). The condensation of (XXX) with the intermediate phosphonium salt (XXI) by means of n-BuLi in THF gives the olefin (XXXI), which is finally hydrogenated and debenzylated with H2 over Pd/C in ethyl acetate.