合成路线1

Treatment of cyclopropane-1,1-dicarboxylic acid (IX) with one equivalent of SOCl2 in the presence of Et3N in THF at 0 °C, followed by condensation of the activated intermediate with 4-fluoroaniline (X), provides the monoamide (XI) , which is optionally chlorinated to (VIII) by treatment with oxalyl chloride in cold THF .
Reaction of 3,4-difluoronitrobenzene (XII) with sodium benzylate prepared from benzyl alcohol and NaH in dimethylacetamide gives 1-benzyloxy-2-fluoro-4-nitrobenzene (XIII) as the main product. Subsequent reduction of compound (XIII) by means of iron and ammonium formate in refluxing toluene leads to the corresponding aniline (XIV), which is subsequently coupled with carboxylic acid (XI) using EDC in CH2Cl2 to afford the diamide (XV). Finally, debenzylation of diamide (XV) by transfer hydrogenation with 1,4-cyclohexadiene and Pd/C in boiling EtOH provides the target intermediate (I) . Scheme 2. Alternatively, acid chloride (VIII) can be directly condensed with 4-amino-2-fluorophenol (XVI) in the presence of 2,6-lutidine in cold THF to give diamide (I) .

合成路线2

AHR-53338 is synthesized in an overall yield of 62% from ethyl isonipecotate (I): Ethyl isonipecotate (I) is protected with benzyl bromide (II) to give (III), which is then treated with 2.5 moles of 4-fluorophenylmagnesium bromide to give the tertiary alcohol (IV). The benzyl group is removed by catalytic hydrogenolysis to give the secondary piperidine (V). The reaction of 1-bromo-3-chloropropane (VI) with acetovanillone (VII) gives 1-[4-(3-chloropropoxy)-3-methoxyphenyl]ethanone (VIII) in excellent yield. A mixture of (V) and (VIII) in 1-butanol and triethylamine heated at reflux yields AHR-53338 isolated as the mandelic acid salt.

合成路线3

The reaction of piperidine-4-carboxylic acid (I) with formic acid and acetic anhydride gives 1-formylpiperidine-4-carboxylic acid (II), which is treated with SOCl2 and acetic anhydride to yield the corresponding acyl chloride (III). The Friedel-Crafts condensation of (III) with refluxing 1,3-difluorobenzene (IV) by means of AlCl3 affords 4-(2,4-difluorobenzoyl)-1-formylpiperidine (V), which is treated with hydroxylamine in refluxing ethanol to give the corresponding oxime (VI). The cyclization of (VI) by means of NaH in hot THF/DMF yields 6-fluoro-3-(1-formylpiperidin-4-yl)-1,2-benzisoxazole (VII), which is treated with HCl in refluxing ethanol to afford 6-fluoro-3-(4-piperidyl)-1,2-benzisoxazole (VIII). Finally, this compound is condensed with 4-(3-chloropropoxy)-3-methoxyacetophenone (IX) by means of K2CO3 in hot DMF. The intermediate 4-(3-chloropropoxy)-3-methoxyacetophenone (IX) can be obtained by condensation of 4-hydroxy-3-methoxyacetophenone (IX) with 3-chcloropropyl bromide (X) by means of NaH or K2CO3 in DMF.

合成路线4

In a related procedure, iodination of acetophenone (XI) gave (XII). Subsequent alkylation of (XII) with dibromoethane afforded bromoethyl ether (XIII), which was converted to sulfide (XIV) by condensation with 4-chlorothiophenol (IX). Mannich reaction of (XIV) with paraformaldehyde and dimethylamine hydrochloride produced tertiary amine (XV), which was quaternized to (XVI) with MeI. Elimination in the resulting ammonium salt (XVI) produced vinyl ketone (XVII). Diketone (XIX) was then obtained by condensation with trimethoxybenzaldehyde (XVIII) in the presence of thiazolium salt (IV). Reduction of both ketone groups of (XIX) using NaBH4 yielded diol (XX), which was further cyclized with orthophosphoric acid in refluxing benzene to furnish a diastereomeric mixture of cis and trans diaryltetrahydrofurans (XXI). Iodine displacement in (XXI) with CuCN produced the corresponding diastereomeric mixture of cyanides, from which the target trans isomer was isolated by column chromatography.

合成路线5

合成路线6

Condensation of 4-hydroxy-3-methoxyacetophenone (XIII) with mesylate (XIV) by means of K2CO3 in DMF at 100 °C yields the aryl ether (XV), which by nitration using HNO3 in AcOH gives the corresponding o-nitroaryl ketone (XVI). Reduction of the nitro group in compound (XVI) using Fe and NH4Cl in refluxing EtOH/H2O gives amine (XVII). Friedlaender cyclization of the o-aminoaryl ketone (XVII) with ethyl formate (XVIII) and NaOMe in DME affords a 4-hydroxyquinoline derivative, which without isolation is chlorinated using POCl3 to produce the corresponding chloride (XIX). Condensation of the aryl chloride (XIX) with 6-hydroxy-N-methyl-1-naphthamide (V) in the presence of DMAP in refluxing dioxane gives adduct (XX), whose methyl ester is hydrolyzed with NaOH in refluxing MeOH to afford acid (XXI). Activation of acid (XXI) with i-BuOCOCl in the presence of DIEA in acetone and subsequent substitution of the obtained mixed anhydride with NaN3 produces azide (XXII), which is finally treated with PhCH2OH in refluxing toluene .

合成路线7

Mitsunobu reaction of apocynin (XIII) with the cyclopropylmethanol derivatives (XIa-c) in the presence of DEAD, PPh3 and DIEA in THF affords the aryl ethers (XXVIIa-c), which by nitration with HNO3 in Ac2O yields the 6-nitrophenyl derivatives (XXVIIIa-c). Condensation of ketones (XXVIIIa-c) with dimethylformamide dimethylacetal (XXIX) in DMF at 100 °C furnishes keto-enamines (XXXa-c), which upon Leimgruber-Batcho reaction using Fe in AcOH at 80 °C produces quinoline derivatives (XXXIa-c). Chlorination of 4-hydroxyquinolines (XXXIa-c) with POCl3 at 85 °C gives their corresponding chlorides (XXXIIa-c). These compounds are alternatively obtained by Mitsunobu condensation of 4-chloro-7-hydroxy-6-methoxyquinoline (XXXIII) with alcohols (Xia-c) using DEAD and PPh3 in CH2Cl2 at 0 °C. Condensation of chlorides (XXXIIa-c) with 6-hydroxy-N-methyl-1-naphthamide (V) by means of DMAP in 2,6-lutidine at 140 °C yields ethers (XIIa-c), whose N-carbamates are cleaved by means of HBr in AcOH .

合成路线8

Alkylation of 4’-hydroxy-3’-methoxyacetophenone (XVII) with benzyl bromide by means of K2CO3 in DMF gives benzyl ether (XVIII), which is reacted with fuming HNO3 and concentrated H2SO4 in cold CH2Cl2 to afford 4’-benzyloxy-5’-methoxy-2’-nitroacetophenone (XIX). After reduction of the nitro group of compound (XIX) using iron powder and ammonium formate in refluxing H2O/toluene, the resulting 2-aminoacetophenone derivative (XX) cyclizes with ethyl formate (XXI) in the presence of NaOEt in DME, providing 7-benzyloxy-6-methoxy-4-quinolinol (XXII). Finally, quinolinol (XXII) is treated with trifluoromethanesulfonyl chloride in the presence of DMAP and 2,6-lutidine in cold CH2Cl2 .