合成路线1

The reaction of the chiral oxazolidinone (I) with (Boc)2O gives the N-protected oxazolidinone (II), which is irradiated with UV light in acetonitrile in the presence of Bu3Sn-SnBu3 and the allylstannane (III) to yield the chiral 5-allyloxazolidinone (IV). Ring cleavage of (IV) by means of Cs2CO3 in methanol affords the N-protected aminoalcohol (V), which is treated with Ms-Cl and TEA in dichloromethane to provide the mesylate (VI). Epimerization of the O-Ms group of (VI) by means of Cs-OAc and 18-crown-6 in refluxing benzene gives the epimeric acetate (VII), which is hydrolyzed with K2CO3 in methanol to yield the N-protected aminoalcohol (VIII). The O-methylation of (VIII) by means of Me-I and Tl-OEt in THF affords the methyl ether (IX), which is N-methylated by means of Me-I and NaH in THF to provide the N-methyl carbamate (X). Finally, the terminal double bond of (X) is oxidated with RuCl3 and NaIO4 in CCl4/acetonitrile/water to furnish the target intermediate, the carboxylic acid (XI) (see scheme no. 149507a, intermediate (VIII)).