合成路线1

Lithiation of dihydrofuran (VIII), followed by the addition of tributylstannyllithium, gave an intermediate (IX) that was quenched with methyl iodide to produce alcohol (X). Silylation of alcohol (X) with tert-butyl dimethylsilyl chloride then gave silyl ether (XI). Copper-catalyzed conjugate addition of the organolithium reagent derived from (XI) to the intermediate enone (VII), with subsequent enolate trapping with triethylsilyl chloride, afforded adduct (XII) as the major diastereoisomer. Epoxidation of the silyl enol ether (XII) with m-chloroperbenzoic acid, followed by selective desilylation using tetrabutylammonium fluoride/ammonium chloride, gave rise to hydroxy ketone (XIII). Methylation of (XIII) in the presence of silver oxide yielded methyl ether (XIV). Then, the keto group of (XIV) was stereoselectively reduced to (XV) employing L-selectride. After protection of the hydroxyl group of (XV) as the benzoate ester, simultaneous deprotection of the ketal and silyl ether functions under acidic conditions provided triol (XVI). Oxidative cleavage of the 1,2-diol moiety of (XVI) with NaIO4 gave ketone (XVII). This was converted to epoxide (XVIII) by stereoselective addition of in situ generated trimethylsulfoxonium ylide.

合成路线2

In a further procedure, 3,5-dimethoxybenzoic acid (X) was converted to the acetophenone (XI) using methyllithium. Treatment of (XI) with phenyltrimethylammonium tribromide provided the dibromoacetophenone (XII) which, upon reaction with morpholine at 55 C, followed by hydrolysis with aqueous HCl, gave the phenylglyoxal (VIII). Alternatively, (VIII) was prepared directly by treating acetophenone (XI) with DMSO and HBr or by oxidation with SeO2. Condensation of the phenylglyoxal (VIII) with methyl glyoxylate hemiacetal (XIII) and ammonium acetate produced the phenylimidazole (XIV), which was protected as the tetrahydrofuranyl derivative (XVI) with dihydrofuran and catalytic p-TsOH. Reduction of the protected imidazole ester (XVI) with LiBH4 provided alcohol (XVII), and then reaction of (XVII) with trichloroacetonitrile in the presence of DBU furnished the acetimidate (XVIII). Finally, the target compound was obtained by reaction of ascomycin (I) with trichloroacetimidate (XVIII) in the presence of fluoboric acid etherate, followed by hydrolytic deprotection.

合成路线3

The cyclization of 2-(3,5-dimethoxyphenyl)glyoxal monohydrate (I) with methyl glyoxylate hemiacetal (II) and ammonium acetate in acetonitrile gives the imidazole derivative (III), which is protected with dihydrofuran (IV) and TsOH, yielding compound (V). The reduction of the ester group of (V) with LiBH4 affords the carbinol (VI), which is esterified with trichloroacetonitrile (VII) to provide the trichloroacetimidate (VIII). The condensation of (VIII) with ascomycin (IX) by means of CF3SO3H in N,N-dimethylpivalamide gives the adduct (X), which is finally deprotected with hot aqueous CF3SO3H.

合成路线4

The cyclization of 2-(3,5-dimethoxyphenyl)glyoxal monohydrate (I) with methyl glyoxylic acid (II) and ammonium acetate in acetonitrile gives the aryl imidazole (III), which is protected with dihydrofuran (IV) and Ts-OH, yielding compound (V). The regioselective lithiation of (V) with n-BuLi, followed by reaction with labeled 14CO2 provides the carboxylic acid (VI), which is esterified with MeI and CaO in DMSO to furnish the methyl ester (VII). The reduction of the ester group of (VII) with LiBH4 affords the carbinol (VIII), which is esterified with trichloroacetonitrile (IX) to provide the trichloroacetimidate (X).

合成路线5

The intermediate succinimidinyl carbonate (XI) has been obtained as follows: The reaction of 2,3-dihydrofuran (XII) with N-iodosuccinimide (NIS) and propargyl alcohol (XIII) in dichloromethane gives trans-3-iodo-2-(propargyloxy)tetrahydrofuran (XIV), which is cyclized by means of Bu3SnH and AIBN in hot toluene yielding the methylenic compound (XV). The ozonolysis of (XV) with O3, followed by reduction with NaBH4 in ethanol affords the racemic alcohol (XVI), which is submitted to an enantioselective acylation with Ac2O and lipase 30 to obtain the chiral alcohol (3R,3aS,6aR)-(XVI). Finally, this compound is treated with disuccinimidinyl carbonate and triethylamine in acetonitrile to provide the target intermediate (XI).

合成路线6

The mixed carbonate ester intermediate (X) has been obtained as follows: The reaction of dihydrofuran (I) with propargyl alcohol (II) and N-iodosuccinimide (NIS) gives the propargyl ether (III), which is cyclized by means of tributyltin hydride and AIBN in refluxing toluene to yield the perhydrofuro[2,3-b]furan (IV). The oxidation of the methylene group of (IV) with ozone in methanol/dichloromethane affords the bicyclic ketone (V), which is reduced with NaBH4 in ethanol to provide racemic (VI). The digestion of (rac)-(VI) with immobilized lipase 30 and acetic anhydride in DME provides a mixture of the (3R)-alcohol (VII) and the (3S)-acetoxy derivative (VIII) that is separated by chromatography. Finally, the (3R)-(VII) alcohol is condensed with disuccinimidyl carbonate (IX) and TEA in acetonitrile to give the target mixed carbonate ester intermediate (X).

合成路线7