合成路线1

Alkylation of 3-hydroxy-4-methoxybenzyl alcohol (I) with 1-bromo-3-methoxypropane (II) gives ether (III). Subsequent conversion of benzyl alcohol (III) into bromide (IV) is carried out using bromotrimetylsilane. The chiral isovaleryloxazolidinone (V) is alkylated with bromide (IV) by means of LiHMDS to afford (VI), which is hydrolyzed to the (S)-2-aryl-2-isopropylpropionic acid (VII) by means of lithium peroxide. The reduction of acid (VII) to the corresponding alcohol with NaBH4/I2 reagent, followed by treatment with PPh3 and NBS, provides bromide (VIII). Alkylation of the chiral dimethoxydihydropyrazin (IX) with bromide (VIII) produces (X). Further hydrolysis of the pyrazine ring of (X) with HCl, followed by Boc protection of the resulting (S,S)-amino ester, yields compound (XI). Reduction of the ester group of (XI) with DIBAL gives aldehyde (XII). This compound is condensed with the Grignard reagent (XIII) to afford the diastereomeric mixture of amino alcohols (XIV). Treatment of mixture (XIV) with 2,2-dimethoxypropane (XV) and TsOH produces a mixture of oxazolidines, from which the required (S,S,S)-isomer (XVI) is isolated by flash chromatography. Hydrogenolitic deprotection of the benzyl ether of (XVI) gives alcohol (XVII).

合成路线2

The intermediate gamma-butyrolactone (XXVIII) has been obtained as follows: Allylation of the imidazolidinone intermediate (V) with allyl bromide (XXI) and LiHMDS in THF gives the chiral intermediate (XXII), which by dihydroxylation and cleavage of the chiral auxiliary with OsO4 and NMMO in tert-butanol/acetone/water yields the lactone alcohol (XXIII). Oxidation of (XXIII) with NaIO4 and RuCl3 in CCl4/acetonitrile/water affords the carboxylic acid (XXIV), which by treatment with (COCl)2 in toluene provides the acyl chloride (XXV). Esterification of (XXV) with benzyl alcohol gives the corresponding benzyl ester as a diastereomeric mixture, from which the desired isomer (XXVI) is separated by flash chromatography. Hydrogenolysis of the benzyl ester (XXVI) with H2 over Pd/C in ethyl acetate yields the carboxylic acid (XXVII), which is treated with oxalyl chloride in toluene to afford the desired gamma-butyrolactone intermediate (XXVIII).

合成路线3

Alternatively, the chiral azido intermediate (XXXIV) can also be synthesized as follows: Alkylation of oxazolidinone (V) with 1-chloro-3-iodopropene (XLVIII) by means of LiHMDS in THF gives compound (XLIX), which is condensed with the magnesium derivative of the phenylpropyl chloride (XXX) to yield, after working up, amide (L). Bromination of (L) with NBS and phosphoric acid affords the bromolactone (LI), which by treatment with NaN3 in tripropylene glycol/water provides the azido derivative (XXXIV).

合成路线4

合成路线5