合成路线1

By condensation of 1-amino-2-methylpyridinium iodide (I) with isobutyric anhydride (II) by means of K2CO3 at reflux temperature.

合成路线2

The acylation of 11beta,16alpha,17alpha,21-tetrahydroxypregna-1,4-diene-3,20-dione (I) with isobutyric anhydride in pyridine gives the 16,17,21-triester (III), which is condensed with cyclohexanecarbaldehyde (IV) by means of HCl and HClO4 in dioxane yielding the cyclic ketal (Va-b) as a diastereomeric mixture. Finally, this mixture is resolved by preparative HPLC over Lichrosorb RP-18 affording the desired (R)-isomer, the target compound. Alternatively, the monoacylation of the ketal 11beta,16alpha,17alpha,21-tetrahydroxypregan-1,4-diene-3,20-dione 16,17-O-cyclohexylmethylene ketal (VI) with isobutyric anhydride (II) by means of K2CO3 in acetone gives the previously described diastereomeric mixture (Va-b), which is resolved by crystallization in ethanol/water.

合成路线3

The intermediate (XIX) can be obtained by two related ways: 1. The condensation of 1,3-dichloroacetone (XIII) with 2,4-difluorobromobenzene (XII) by means of n-BuLi gives 1,3-dichloro-2-(2,4-difluorophenyl)-2-propanol (XIV), which is converted into the epoxide (XV) by reaction with KOH in toluene. The reaction of (XV) with isobutyric anhydride (XXII) yields the diester (XX), which is stereoselectively hydrolyzed with Lipase D in an acetate buffer to afford the (R)-monoester (XXIV). The reaction of (XXIV) with Ms-Cl and pyridine provides the monomesylate (XXV), which is treated with KOH in toluene to give the hydroxymethyl epoxide (XVII). Finally, this compound is treated with 1,2,4-triazole (XVIII) and K2CO3 in refluxing THF to afford the target intermediate. Alternatively, the mesylate (XXV) can be treated with 1,2,4-triazole (XVIII) and Na2CO3 in refluxing methanol to yield directly the target intermediate (XIX). 2. The acylation of 1,3-dihydroxypropanone (XXI) with butyric anhydride (XXII), pyridine and DMAP gives the diester (XXIII), which is submitted to a Grignard condensation with 2,4-difluorobromobenzene (XIII) by means of Mg to afford the already described intermediate, the diester (XIX).

合成路线4

The demethylation of galanthamine (I) with ethyl mercaptane sodium salt in hot DMF gives 6-demethylgalanthamine (II), which is selectively monoesterified at the phenolic OH with N-methylcarbamic acid and CDI yielding the monoester (III). Finally this compound is esterified again at the remaining OH with isobutyric anhydride (IV) and TEA or DMAP affording the target diester. The selective monoesterification of (II) can also be performed with N-methylcarbamic anhydride and TEA or DMAP, with N-methylcarbamoyl chloride and DBU, or with N-methylisocyanate and K2CO3.

合成路线5

Treatment of 6-deoxy-6-chloroganciclovir (I) with trimethylamine in DMF-THF at low temperature produced the trimethylammonium salt (II), which was subsequently displaced with KF in DMF at 80 C under vacuum removal of the Me3N to afford the corresponding 6-fluoro derivative (III). Finally, monoacylation with one equivalent of isobutyric anhydride (IV) in the presence of DMAP provided the target ester.

合成路线6

Compound (XI) was condensed with methyl benzyl amine (XII) to furnish tertiary amine (XIII). The nitro group of (XIII) was then reduced with iron powder and HCl to afford amine (XIV). Subsequent acylation of (XIV) with isobutyric anhydride (XV) in the presence of Et3N produced amide (XVI). The title compound was then obtained by transesterification between (XVI) and titanium isopropoxide in isopropanol, followed by treatment with ethanolic HCl.

合成路线7

合成路线8

合成路线9