合成路线1

(S)-2-(Allyloxycarbonylamino)-3-[4-methoxy-3,5-bis(tert-butyldimethylsilyloxy)phenyl]propionic acid methyl ester (scheme 13922101a, cp. (IX)). The silylation of 3,5-dihydroxy-4-methoxybenzoic acid methyl ester (XXXII) with TBDMS-Cl, TEA and DMAP in dichloromethane gives the silylated compound (XXXIII), which is reduced with DIBAL in dichloromethane yielding the corresponding benzyl alcohol (XXXIV). The oxidation of (XXXIV) with pyridinium dichromate (PDC) in dichloromethane affords the benzaldehyde (XXXV), which is condensed with malonic acid monomethyl ester (XXXVI) by means of piperidine/AcOH in toluene providing the corresponding benzylidene derivative (XXXVII). The reaction of (XXXVII) with (PhO)2PO-N3 and benzyl alcohol in hot toluene affords the benzyloxycarbonylamino derivative (XXXVIII), which is enantioselectively reduced with H2 over a chiral Rh catalyst in methanol providing and (S)-2-(benzyloxycarbonylamino)-3-[4-methoxy-3,5-bis(tert-butyldimethylsilyloxy)phenyl]propionic acid methyl ester (XXXIX). Elimination of the benzyl protecting group of (XXXIX) with H2 over Pd/C in ethyl acetate gives the free aminoester (XL), which is finally reprotected with allyl chloroformate (XLI) and pyridine to furnish the desired intermediate (IX).