合成路线1

Racemic cyclohexylphenyl glycolic acid (CHPGA) (I) is dissolved with (L)-tyrosine methyl ester (II) in refluxing acetonitrile/water to yield a mixture of diastereomeric salts, which is resolved by crystallization to afford the desired diastereomeric salt [(S)-CHPGA-(L)-TME] (III). Finally, the hydrolysis of salt (III) with HCl or H2SO4 at 40-50ºC in toluene yields the enantiomer (IV). Alternatively intermediate (IV) can be obtained as follows: acetalization of (S)-mandelic acid (V) with pivaldehyde (VI) in pentane and catalytic TfOH provides derivative (VII), which is then treated with LHMDS and then condensed with cyclohexanone (VIII) in THF to furnish aldol adduct (IX). Elimination of tertiary alcohol in (IX) with SOCl2 and pyridine in THF gives derivative (X), which is then converted into intermediate (IV) either by first hydrolysis of lactone (X) with KOH in MeOH and subsequent hydrogenation of the obtained derivative (XI) over Pd/C in MeOH, or by first hydrogenation of (X) over Pd/C in MeOH to give (XII), followed by hydrolysis with KOH in MeOH. On turn, derivative (XII) can alternatively be synthesized by treatment of derivative (VII) with LHMDS, followed by reaction with 3-bromocyclohexene (XIII) in THF to provide derivative (XIV), which is then hydrogenated over Pd/C.