合成路线1

The cyclization of 2-hydroxyacetophenone (I) with pyruvic aldehyde dimethylacetal (II) by means of pyridine in refluxing toluene gives 2-(dimethoxymethyl)-2-methyl-3,4-dihydro-2H-1-benzopyran-4-one (III), which is nitrated with ammonium nitrate and TFA yielding the 6-nitro derivative (IV). The reduction of (IV) with NaBH4 in methanol affords the benzopyranol (V), which is treated with MsCl and DIEA to provide the mesylate (VI). The reaction of (VI) with DBU in refluxing toluene gives 2-(dimethoxymethyl)-2-methyl-6-nitro-2H-1-benzopyran (VII), which is treated with NBS in DMSO to yield the bromohydrin (VIII). Epoxidation of (VIII) with NaOH in dioxane/water affords the epoxide (IX), which is treated with 2-pyrrolidinone (X) and potassium tert-butoxide in tert-butanol to furnish 1-[2-(dimethoxymethyl)-3-hydroxy-2-methyl-3,4-dihydro-2H-1-benzpyran-4-yl]pyrrolidin-2-one (XI). The trans-acetalization of (XI) with ethylene glycol (XII) and TsOH in refluxing toluene gives the 1,3-dioxolanyl derivative (XIII), which is finally dehydrated to the target compound with NaOH in refluxing dioxane.