Acetic acid--water (1/1) → 4-(2-Amino-6-chloro-9H-purin-9-yl)-2-cyclopentene-1-methanol, (1S,4R)-

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Reaction Conditions

Reaction Steps

A suspension of (1S, 4R)-4-((2-Amino-6-chloro-5-((4chlorophenyl)azo)4-pyrimidinyl)amino)-2-cyclopentene-1-methanol hydrate (1.96 g, 5 mmol) in tetrahydrofuran (15 mL) was treated with acetic acid/water (1:1, 5 mL), then with zinc dust (1.63 g, 25 mmol) in portions so as to keep the pot temperature below 35° C. The deep yellow color faded after 10 min. and after an additional 50 min the solution was filtered to remove precipitated zinc salts. The filter cake was rinsed with tetrahydrofuran and the filtrate was refiltered to remove additional zinc salts, then concentrated in vacuo with addition of toluene to facilitate removal of water and acetic acid. The residue was rinsed with toluene/hexane to separate some of the 4-chloroaniline byproduct, taken up in triethyl orthoformate (40 mL), cooled on an ice bath (5° C.), and treated dropwise with concentrated hydrochloric acid (1.9 mL). The mixture was stirred at 5° C. for 5 h (tan suspension soon formed), slowdy warmed to room temperature, and stirred for an additional 18 h, then cooled on an ice bath and filtered. The filter cake was rinsed with ether (save filtrate), and this solid was taken up in water (30 mL), filtered, and the solids washed with water. The aqueous filtrate was basifled with sodium carbonate to pH-9, then extracted with 5% isopropanol-chloroform (3×25 mL). The combined extracts were dried (Na2SO4) and concentrated in vacuo to a residual tan foam (0.85 g). The organic filtrate from above wasconcentrated in vacuoand the residue taken up in 1 N hydrochloric acid (30 mL), sti rred for 1 h, filtered, and the filtrate adjusted to pH-6 with 5 N sodium hydroxide (6 mL), then basified with sodium carbonate. This aqueous suspension was extracted with 5% isopropanol-chloroform (3×25 mL), and the combined organic extracts were dried (Na2SO4) and concentrated in vacua to a tan foam (0.55 g). The two batches were combined, dissolved in warm chloroform, and loaded onto a silica gel column, which was eluted with 7% methanol-chloroform to afford pure fractions containing the subject compounds. These were concentrated in vacua and the residual foam crystallized from ethyl acetate (2 crops) to afford 0.869 (65%) of the title compound as a pale tan solid; mp 160-162° C. 1H-NMR(DMSO-d6) δ: 8.04 (s, 1H); 6.91 (s, 2H); 6.15 (m, 1H); 5.90 (m, 1H); 5.45 (m, 1H); 4.73 (t, 1H, J=5 Hz); 3.45 (t, 2H, J=5 Hz; 2.80-2.95 (m, 1H); 2.55-2.70 (m, 1H); 1.60-1.70 (m, 1H ). Ms (Cl): m/z 170 (m-C5 ring, 100); 230 (m-Cl, 50); 266 (m+H+, 100). [α]20589−104°, [α]20436−267° (c=0.29, methanol).

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