合成路线1

The alkylation of 4(S)-benzyl-3-(4-methylpentanoyl)oxazolidin-2-one (I) with allyl bromide (II) by means of lithium diisopro-pylamide (LDA), followed by hydrolysis with LiOOH gives the chiral pentenoic acid (III), which is treated with dimethylamine and cyanophosphonic acid diethyl ester yielding the dimethylamide (IV). The iodination of (IV) with I2/dimethoxyethane (DME) with simultaneous cyclization yields 5(S)-(iodomethyl)-3(R)-isobutyltetrahydrofuran-2-one (V). The condensation of (V) with thioacetic acid by means of NaH, followed by a reductive cleavage and tritylation with triphenylmethanol and TFA affords 3(R)-isobutyl-5(S)-(triphenylmethylsulfanylmethyl)tetrahydrofuran-2-one (VI). The ring opening of (VI) with NaOH, follwed by silylation with tert-butyldimethylsilyl chloride gives 4(S)-(tert-butyldimethylsilyloxy)-2(R)-isobutyl-5-(tritylsulfanyl)pentanoic acid (VII), which is condensed with 2(S)-amino-N,3,3-trimethylbutyramide (VIII) by means of cyanophosphonic acid diethyl ester and desilylated with tetrabutylammonium fluoride to yield 2(S)-[2(R)-isobutyl-4-(S)-hydroxy-5-(tritylsulfanyl)pentanamido]-N,3,3-trimethylbutyramide (IX). Finally, this compound is detritylated with trifluoroacetic acid (TFA) to afford the target campound (X).