合成路线1

Friedel-Crafts reaction between 4-hydroxyphenylacetic acid (I) and resorcinol (II) by means of BF3.Et2O provides trihydroxydeoxy benzoin (III), which is then protected with dihydropyran (IV) in the presence of TsOH to give the bis-THP ether (V). Knoevenagel reaction of (V) with 4-hydroxybenzaldehyde (VI) in the presence of piperidine in refluxing benzene, followed by alkylation with 1-(2-chloroethyl)piperidine (VII) in the presence of Cs2CO3 in refluxing acetone:H2O to yield chromanone (VIII). Alternatively, (VIII) can be synthesized by reaction of (V) with compound (IX) (obtained in turn from reaction between aldehyde (VI) and chloro derivative (VII) with K2CO3 in DMF) by means of piperidine in refluxing toluene, followed by treatment with NaOAc in refluxing MeOH. Chromanone (VIII) is then alkylated either with MeLi or with methylmagnesium bromide in THF and then dehydrated and deprotected in HOAc furnishing chromene (X). Racemic compound (X) is then resolved to afford enantiomer (XI) either by preparative chiral HPLC or by chemical resolution of the corresponding diastereomeric salt obtained by reaction with (+)-CSA in DMF/CH2Cl2, and treatment of the resulting salt with saturated K2CO3 . Finally, the target product is obtained by acylation of (XI) by reaction with pivaloyl chloride (XII) and Et3N in CH2Cl2.