The Grignard reaction of the protected epoxide (I) with 4-(dimethylamino)phenylmagnesium bromide (II) gives the 11-substituted compound (III), which is submitted to an Oppenhauer oxidation with cyclohexanone and aluminum isopropoxide yielding the 17-keto derivative (IV). The photochemical epimerization of the 13beta-methyl of (IV) with a high pressure mercury lamp in dioxane affords the epimer (V), which is condensed with 1-tetrahydropyranyloxy-2-propyne (VI) by means of butyllithium in THF to give the acetylenic alcohol (VII). Finally, this compound is reduced with hydrogen over Pd/C in ethanol and deprotected and dehydrated by treatment with hot aqueous acetic acid.

The Wittig condensation of 2-phenylpyrazolo[1,5-a]pyridine-3-carboxaldehyde (I) with trimethylphosphonoacetic acid methyl ester (II) by means of NaH in hot toluene gives 3(E)-(2-phenylpyrazolo[1,5-a]pyridin-3-yl)acrylic acid methyl ester (III), which is hydrolyzed with NaOH in methanol - water yielding the corresponding free acid (IV). The reaction of (IV) with SOCl2 in DMF affords the acyl chloride (V), which is finally condensed with 2(R)-(2-hydroxyethyl)piperidine (VI) by means of bis(trimethylsilyl)acetamide and triethylamine in dichloromethane.

FK-352 can be obtained by two related ways: 1) The Wittig condensation of 2-phenylpyrazolo[1,5-a]pyridine-3-carbaldehyde (I) with trimethyl phosphonoacetate (II) by means of NaH in hot toluene gives 3-(2-phenylpyrazolo[1,5-a]pyridin-3-yl)-2(E)-propenoic acid methyl ester (III), which by hydrolysis with aqueous NaOH yields the expected free acid (IV) (1). The reaction of (IV) with SOCl2 and DMF in dichloromethane affords the corresponding acyl chloride (V), which is condensed with 2-[2(R)-piperidinyl]acetic acid ethyl ester (VI) by means of triethylamine in dichloromethane affording the acylated piperidine (VII). Finally, this compound is hydrolyzed with NaOH in refluxing methanol. 2) The free acid precursor (IV) can also be obtained by condensation of 2-phenylpyrazolo[1,5-a]pyridine (VIII) with 3-(dimethylamino)acrylic acid ethyl ester (IX) by means of AlCl3 in methylene chloride giving the ethyl ester (X), which is hydrolyzed to the free acid (IV) by treatment with aqueous NaOH.

The Grignard reaction of the protected epoxide (I) with 4-(dimethylamino)phenylmagnesium bromide (II) gives the 11-substituted compound (III), which is submitted to an Oppenhauer oxidation with cyclohexanone and aluminum isopropoxide yielding the 17-keto derivative (IV). The photochemical epimerization of the 13beta-methyl of (IV) with a high pressure mercury lamp in dioxane affords the epimer (V), which is condensed with 1-tetrahydropyranyloxy-2-propyne (VI) by means of butyllithium in THF to give the acetylenic alcohol (VII). Finally, this compound is reduced with hydrogen over Pd/C in ethanol and deprotected and dehydrated by treatment with hot aqueous acetic acid.

The Grignard reaction of the protected epoxide (I) with 4-(dimethylamino)phenylmagnesium bromide (II) gives the 11-substituted compound (III), which is submitted to an Oppenhauer oxidation with cyclohexanone and aluminum isopropoxide yielding the 17-keto derivative (IV). The photochemical epimerization of the 13beta-methyl of (IV) with a high pressure mercury lamp in dioxane affords the epimer (V), which is condensed with 1-tetrahydropyranyloxy-2-propyne (VI) by means of butyllithium in THF to give the acetylenic alcohol (VII). Finally, this compound is reduced with hydrogen over Pd/C in ethanol and deprotected and dehydrated by treatment with hot aqueous acetic acid.

The Grignard reaction of the protected epoxide (I) with 4-(dimethylamino)phenylmagnesium bromide (II) gives the 11-substituted compound (III), which is submitted to an Oppenhauer oxidation with cyclohexanone and aluminum isopropoxide yielding the 17-keto derivative (IV). The photochemical epimerization of the 13beta-methyl of (IV) with a high pressure mercury lamp in dioxane affords the epimer (V), which is condensed with 1-tetrahydropyranyloxy-2-propyne (VI) by means of butyllithium in THF to give the acetylenic alcohol (VII). Finally, this compound is reduced with hydrogen over Pd/C in ethanol and deprotected and dehydrated by treatment with hot aqueous acetic acid.