A representative procedure is shown in Scheme 1.

As shown in Scheme 1, conversion of the C-42 hydroxyl of rapamycin to a trifluoromethanesulfonate or fluorosulfonate leaving group provided A. Displacement of the leaving group with tetrazole in the presence of a hindered, non-nucleophilic base, such as 2,6-lutidine, or, preferably, diisopropylethyl amine provided epimers B and C, which were separated and purified by flash column chromatography.

Synthetic Methods

The foregoing may be better understood by reference to the following examples which illustrate the methods by which the compounds of the invention may be prepared and are not intended to limit the scope of the invention as defined in the appended claims.

Example 1 42-Epi-(tetrazolyl)-rapamycin (less polar isomer) Example 1AA solution of rapamycin (100 mg, 0.11 mmol) in dichloromethane (0.6 mL) at −78° C. under a nitrogen atmosphere was treated sequentially with 2,6-lutidine (53 uL, 0.46 mmol, 4.3 eq.) and trifluoromethanesulfonic anhydride (37 uL, 0.22 mmol), and stirred thereafter for 15 minutes, warmed to room temperature and eluted through a pad of silica gel (6 mL) with diethyl ether. Fractions containing the triflate were pooled and concentrated to provide the designated compound as an amber foam.

Example 1B 42-Epi-(tetrazolyl)-rapamycin (less polar isomer)A solution of Example 1A in isopropyl acetate (0.3 mL) was treated sequentially with diisopropylethylamine (87 L, 0.5 mmol) and 1H-tetrazole (35 mg, 0.5 mmol), and thereafter stirred for 18 hours. This mixture was partitioned between water (10 mL) and ether (10 mL). The organics were washed with brine (10 mL) and dried (Na₂SO₄). Concentration of the organics provided a sticky yellow solid which was purified by chromatography on silica gel (3.5 g, 70-230 mesh) eluting with hexane (10 mL), hexane:ether (4:1(10 mL), 3:1(10 mL), 2:1(10 mL), 1:1(10 mL)), ether (30 mL), hexane:acetone (1:1(30 mL)). One of the isomers was collected in the ether fractions.

MS (ESI) m/e 966 (M)⁻;

Example 2 42-Epi-(tetrazolyl)-rapamycin (more polar isomer) Example 2A 42-Epi-(tetrazolyl)-rapamycin (more polar isomer)Collection of the slower moving band from the chromatography column using the hexane:acetone (1:1) mobile phase in Example 1B provided the designated compound.

MS (ESI) m/e 966 (M)⁻.

………………………………………………….

US20100204466

sirolimus (commercially available or produced as described ((Paiva et al., 1991; Sehgal et al., 1975; Vezina et al., 1975) is dissolved in DCM:toluene (such as 1:2) 100. The reaction mixture is concentrated to dryness 105, and the azeo-drying process 105 is repeated 1-5 times more, more preferably 2-4 times, most preferably twice, preferably with DCM:toluene. The resulting foamy solid is dissolved in IPAc 110, and then 2,6-Lutidine is added 115. The solution is cooled to −30° C. 115. Triflic anhydride is then slowly added to the solution 115. After stirring the reaction mixture, the solution is filtered under nitrogen. The recovered salts 120 are washed with IPAc 125.

To the salts is added 1-H-tetrazole and DIEA 130. The reaction mixture is stirred at room temperature (e.g., 22-25° C.) 135and then concentrated. The crude reaction mixture is purified, using for example, a silica gel column and using, e.g., 1:1 THF:heptane to elute 140. The fractions are monitored for the N-1 isomer (which elutes more slowly than the N-2 isomer), pooled and concentrated, forming an oil. The oil is dissolved in minimum DCM and the solution loaded on a silica gel column packed in, for example, 65:35 heptane:acetone 145. The column is eluted with, for example, 65:35 heptane:acetone, the fractions monitored for the pure product, pooled and concentrated 150.

The purified product is then dissolved in t-BME, and then n-heptane is slowly added to form a precipitate while vigorously stirring the solution 150. The precipitated solids are stirred at 5-10° C., filtered, washed again with heptane, and dried on the funnel with nitrogen. The product is dissolved in acetone and treated with BHT 155. The solution is concentrated, dissolved in acetone, and then concentrated to dryness. The product is then dried under vacuum at 47° C. 160.

EXAMPLES

Example 1 Dichloromethane-Toluene Isopropylacetate One-Pot Process with Filtration (1)

In this example, zotarolimus was prepared from rapamycin in a one-pot process using dichloromethane, toluene and isopropylacetate; the preparation was then purified, concentrated, and dried. The purified product was then characterized by its ¹H, ¹³C NMR resonances from COSY, ROESY, TOCSY, HSQC, and HMBC spectra.

Rapamycin (10 g) was dissolved in dichloromethane (DCM, 25 ml) and toluene (50 ml). The reaction mixture was concentrated to dryness. This azeo-drying process was repeated twice with DCM/toluene. The foamy solid was dissolved in isopropylacetate (IPAc, 65 ml), and 2,6-Lutidine (3.2 ml) was added. The solution was cooled to −30° C. acetonitrile-dry ice bath, and triflic anhydride (2.8 ml) was added slowly in 10 minutes. The reaction mixture was stirred for 30 minutes, and then filtered under nitrogen atmosphere. The salts were washed with IPAc (10 ml). 1-H-tetrazole (2.3 g), followed by diisopropylethylamine (DIEA, 7.4 ml) were added. The reaction mixture was stirred for 6 hours at room temperature, and then concentrated. The crude reaction mixture was purified on a silica gel column (350 g) eluting with 1:1 THF/heptane. The fractions containing product that eluted later (predominantly N-1 isomer) were collected and concentrated. The concentrated oil was dissolved in minimum DCM and loaded on a silica gel column packed in 65:35 heptane:acetone. The column was eluted with 65:35 heptane:acetone, and fractions containing pure product were concentrated.

The purified product was then dissolved in t-butylmethyl ether (t-BME, 13.5 g), and n-heptane (53 g) was added slowly with vigorous stirring. The precipitated solids were stirred at 5-10° C. for 2 hours, filtered, washed with heptane and dried on the funnel with nitrogen to give 3.2 g wet product. The solids (1.0 g) were dissolved in acetone (10 ml) and treated with 2,6-di-tert-butyl-4-ethylphenol (DEP, 0.2%). The solution was concentrated, dissolved in acetone (10 ml) and concentrated to dryness. The product was dried under vacuum for 18 hours at 47° C., yielding 0.83 g of zotarolimus. The product was characterized by its ¹H, ¹³C NMR resonances from its COSY, ROESY, TOCSY, HSQC, and HMBC spectra.

¹H-NMR (DMSO-d6, position in bracket): ppm 0.73 (Me, 43); 0.81 (Me, 49); 0.84 (Me, 46); 0.89 (Me, 48); 0.98 (Me, 45); 1.41, 1.05 (CH2, 24); 1.18, 1.10 (CH2, 36); 1.52 (CH, 37); 1.53 (CH2, 12 & 42); 1.59, 1.30 (CH2, 5); 1.41, 1.67 (CH2, 4); 1.11, 1.73 (CH2, 38); 1.21, 1.83 (CH2, 15); 1.21, 1.83 (CH2, 13); 1.62 (Me, 44); 1.73 (Me, 47); 1.76 (CH, 35); 1.60, 2.09 (CH2, 3); 1.93, 2.21 (CH2, 41); 2.05 (CH, 11); 2.22 (CH, 23); 2.47 (CH, 25); 2.40, 2.77 (CH2, 33); 3.06 (OCH3, 50); 3.16 (OCH3, 51); 3.22, 3.44 (CH2, 6); 3.29 (OCH2, 52); 3.29 (CH, 31); 3.60 (CH, 39), 3.62 (CH, 16); 3.89 (CH, 27); 4.01 (CH, 14); 4.02 (CH, 28); 4.95 (CH, 2); 5.02 (CH, 34); 5.10 (═CH, 30); 5.17 (CH, 40); 5.24 (OH, 28); 5.46 (═CH, 22); 6.09 (═CH, 18); 6.15 (═CH, 21); 6.21 (═CH, 20); 6.42 (═CH, 19); 6.42 (OH, 10), 9.30 (CH, 53).

¹³C NMR (DMSO-d6, position in bracket): ppm 10.4 (Me, 44); 13.1 (Me, 47); 13.6 (Me, 46); 14.5 (Me, 49); 15.5 (Me, 43 & 48); 20.3 (CH2, 4); 21.6 (Me, 45); 24.4 (CH2, 4); 26.2 (CH2, 12); 26.4 (CH2, 3); 26.8 (CH2, 41); 27.2 (CH2, 42); 29.6 (CH2, 13); 31.6 (CH2, 38), 31.7 (CH, 37); 32.9 (CH, 35); 34.8 (CH, 11); 35.2 (CH, 23); 38.2 (CH2, 36); 39.1 (CH, 25); 39.4 (CH2, 33); 39.6 (CH2, 24), 40.0 (CH2, 15); 43.4 (CH2, 6); 45.2 (CH, 31); 50.6 (CH, 2); 55.4 (OCH3, 50); 55.8 (OCH3, 52); 57.0 (OCH3, 52); 55.9 (CH, 40); 66.2 (CH, 14); 73.4 (CH, 34); 75.6 (CH, 28); 77.4 (CH, 39); 82.3 (CH, 16); 85.7 (CH, 27); 99.0 (CH, 10); 125.3 (═CH, 30); 127.0 (═CH, 18 & 19); 130.4 (═CH, 21); 132.2 (═CH, 20); 137.2 (═CMe, 29); 137.7 (═CMe, 17); 139.2 (═CH, 22); 144.6 (CH, 53); 167.0 (C═O, 8); 169.1 (C═O, 1); 199.0 (C═O, 9); 207.5 (C═O, 32); 210.7 (C═O, 26).

Example 2 Dichloromethane-Isopropylacetate One-Pot Process (2)

In this example, zotarolimus was prepared from rapamycin in a one-pot process using dichloromethane and isopropylacetate. The compound was then purified, concentrated, and dried.

Rapamycin (10 g) was dissolved in dichloromethane (DCM, 100 g). 2,6-Lutidine (2.92 g) was added. The solution was cooled to −30° C. in acetonitrile-dry ice bath, and triflic anhydride (4.62 g) was added slowly in 10 minutes. The reaction mixture was stirred for 20 minutes, and then warmed to 10° C. within 15 minutes. The reaction solution was then concentrated. The residue was dissolved in IPAc (55 g). 1-H-tetrazole (2.68 g), followed by diisopropylethylamine (DIEA, 7.08 g) were then added. The reaction mixture was stirred for 6 hours at room temperature and then concentrated. The crude reaction mixture was purified on a silica gel column (360 g), eluting with 1:1 THF:heptane. The fractions containing product that eluted later (principally N-1) were collected and concentrated. The concentrated oil was dissolved in minimum DCM and loaded on a silica gel column (180 g) that was packed in 65:35 heptane:acetone. The column was then eluted with 65:35 heptane:acetone, and fractions containing pure product were concentrated.

The purified product was dissolved in t-butylmethyl ether (t-BME, 23 g) and added slowly to n-heptane (80 g) with vigorous stirring. The precipitated solids were stirred at 5-10° C. for not longer than 1 hour, filtered, washed with heptane and dried on the funnel with nitrogen. BHT (0.015 g) was added to the solids. The solids were dissolved in acetone (20 g), passed through a filter, and concentrated. The residue was treated with acetone two times (20 g), and concentrated each time to dryness. The product was then dried under vacuum for 18 h at not more than 50° C. to give 2.9 g of zotarolimus.

Example 3 Dichloromethane One Pot Process (3)

In this example, zotarolimus was prepared from rapamycin in a one-pot process using dichloromethane. The compound was then purified, concentrated, and dried as described in Example 2.

Rapamycin (7.5 g) was dissolved in DCM (30 g). 2,6-Lutidine (1.76 g) was added. The solution was cooled to −30° C. in acetonitrile-dry ice bath, and triflic anhydride (2.89 g) was added slowly in 10 minutes. The reaction mixture was stirred for 20 minutes, and then assayed for the presence of rapamycin to determine consumption in the reaction. 1-H-tetrazole (1.44 g), followed by DIEA (5.29 g) was added. The reaction mixture was stirred for 6 hours at room temperature, and then directly loaded on a silica gel (270 g) column prepared in 1:1 THF:n-heptane (v/v). The crude reaction mixture was purified with 1:1 THF:n-heptane. The fractions containing product that elute later were collected and concentrated. The concentrated solids were dissolved in minimum DCM and loaded on a silica gel column (135 g) packed in 70:30 n-heptane:acetone. The column was eluted with 70:30 n-heptane:acetone, and fractions containing pure product, as identified by thin-layer chromatography (TLC), were concentrated.

The purified product was dissolved in t-BME (9 g), and added slowly to n-heptane (36 g) with vigorous stirring at 10±10° C. The precipitated solids were stirred at 5-10° C. for not longer than 1 hour, filtered, washed with n-heptane and dried on the funnel with nitrogen. BHT (0.006 g) was added to the solids. The solids were dissolved in acetone (20 g), passed through a filter, and concentrated. The residue was treated with acetone twice (20 g each) and concentrated each time to dryness. The product was dried under vacuum for not longer than 18 hours at not more than 50° C. to give 2.5 g of zotarolimus.

The above process, when carried out with rapamycin presence of 2,6-di-tert-butylpyridine or 2,4,6-collidine (2,3,5-trimethylpyridine) as a non-nucleophilic in step 1a gave zotarolimus of acceptable purity, but a lower yield.

Example 4 High-Pressure Liquid Chromatography HPLC Purification of Zotarolimus Prepared by the One-Pot Synthesis Method

In this example, zotarolimus was made from rapamycin using a one-pot synthesis method of the invention (using DCM), and then subjected to an additional round of purification using HPLC.

Rapamycin (3.75 g) was dissolved in dichloromethane (DCM, 15 g). 2,6-Lutidine (0.88 g) was then added. The solution was cooled to −30° C. in acetonitrile-dry ice bath, and triflic anhydride (1.45 g) was added slowly in 10 minutes. The reaction mixture was stirred for 20 minutes, and then 1-H-tetrazole (0.72 g), followed by DIEA (2.65 g) was added. The reaction mixture was stirred for 6 hours at 25° C., and then directly loaded on a silica gel (115 g) column prepared in 70:30 n-heptane:acetone. The crude reaction mixture was purified with 70:30 n-heptane:acetone. The fractions containing product were collected, and concentrated.

The concentrated solids were dissolved in acetonitrile-water and loaded on a C-18 TechniKrom column (5 cm×25 cm), and eluted with 64:36 acetonitrile-water containing 0.1% BHT. Fractions were analyzed by reverse phase (RP)—HPLC, and product fractions pooled and concentrated to remove acetonitrile. The product was extracted with ethyl acetate or isopropyl acetate, dried (sodium sulfate) and concentrated.

The purified product was dissolved in t-BME (4.5 g), and added slowly to n-heptane (18 g) with vigorous stirring at −10° C. The precipitated solids were stirred at 5-10° C. for not longer than 1 hour, filtered, washed with n-heptane and dried on the funnel with nitrogen. BHT (0.005 g) was added to the solids. The solids were dissolved in acetone (20 g), passed through a filter, and concentrated. The residue was treated with acetone twice (20 g), and concentrated each time to dryness. The product was dried under vacuum for not longer than 18 hours at not more than 50° C. to give 1.2 g of high quality zotarolimus.